publicationDate,title,abstract,id
2013-02-18,Comparative Measurements of Inverse Spin Hall and Magnetoresistance in YIG|Pt and YIG|Ta,"We report on a comparative study of spin Hall related effects and
magnetoresistance in YIG|Pt and YIG|Ta bilayers. These combined measurements
allow to estimate the characteristic transport parameters of both Pt and Ta
layers juxtaposed to YIG: the spin mixing conductance $G_{\uparrow \downarrow}$
at the YIG$|$normal metal interface, the spin Hall angle $\Theta_{SH}$, and the
spin diffusion length $\lambda_{sd}$ in the normal metal. The inverse spin Hall
voltages generated in Pt and Ta by the pure spin current pumped from YIG
excited at resonance confirm the opposite signs of spin Hall angles in these
two materials. Moreover, from the dependence of the inverse spin Hall voltage
on the Ta thickness, we extract the spin diffusion length in Ta, found to be
$\lambda_{sd}^\text{Ta}=1.8\pm0.7$ nm. Both the YIG|Pt and YIG|Ta systems
display a similar variation of resistance upon magnetic field orientation,
which can be explained in the recently developed framework of spin Hall
magnetoresistance.",1302.4416v1
2023-12-17,Cryogenic hybrid magnonic circuits based on spalled YIG thin films,"Yttrium iron garnet (YIG) magnonics has sparked extensive research interests
toward harnessing magnons (quasiparticles of collective spin excitation) for
signal processing. In particular, YIG magnonics-based hybrid systems exhibit
great potentials for quantum information science because of their wide
frequency tunability and excellent compatibility with other platforms. However,
the broad application and scalability of thin-film YIG devices in the quantum
regime has been severely limited due to the substantial microwave loss in the
host substrate for YIG, gadolinium gallium garnet (GGG), at cryogenic
temperatures. In this study, we demonstrate that substrate-free YIG thin films
can be obtained by introducing the controlled spalling and layer transfer
technology to YIG/GGG samples. Our approach is validated by measuring a hybrid
device consisting of a superconducting resonator and a spalled YIG film, which
gives a strong coupling feature indicating the good coherence of our system.
This advancement paves the way for enhanced on-chip integration and the
scalability of YIG-based quantum devices.",2312.10660v2
2019-01-08,Fabrication of yttrium-iron-garnet/Pt multilayers for the longitudinal spin Seebeck effect,"For longitudinal spin Seebeck effect (LSSE) devices, a multilayer structure
comprising ferromagnetic and nonmagnetic layers is expected to improve their
thermoelectric power. In this study, we developed the fabrication method for
alternately stacked yttrium-iron-garnet (YIG)/Pt multilayer films on a
gadolinium gallium garnet (GGG) (110) substrate, GGG/[YIG(49 nm)/Pt(4 nm)]$_n$
($n =$ 1 - 5) based on room-temperature sputtering and $ex$-$situ$
post-annealing method and we evaluated their structural and LSSE properties.
The fabricated [YIG/Pt]$_n$ samples show flat YIG/Pt interfaces and almost
identical saturation magnetization $M_{\rm s}$, although they contain
polycrystalline YIG layers on Pt layers as well as single-crystalline YIG
layers on GGG. In the samples, we observed clear LSSE signals and found that
the LSSE thermoelectric power factor (PF) increases monotonically with
increasing $n$; the PF of the [YIG/Pt]$_5$ sample is enhanced by a factor of
$\sim 28$ compared to that of [YIG/Pt]$_1$. This work may provide a guideline
for developing future multilayerbased LSSE devices.",1901.02129v1
2013-01-25,Intrinsic Spin Seebeck Effect in Au/YIG,"The acute magnetic proximity effects in Pt/YIG compromise the suitability of
Pt as a spin current detector. We show that Au/YIG, with no anomalous Hall
effect and a negligible magnetoresistance, allows the measurements of the
intrinsic spin Seebeck effect with a magnitude much smaller than that in
Pt/YIG. The experiment results are consistent with the spin-polarized
density-functional calculations for Pt with a sizable and Au with a negligible
magnetic moment near the interface with YIG.",1301.6164v1
2014-10-05,Planar Hall effect in Y3Fe5O12(YIG)/IrMn films,"The planar Hall effect of IrMn on an yttrium iron garnet (YIG = Y3Fe5O12) was
measured in the magnetic field rotating in the film plane. The magnetic field
angle dependence of planar Hall resistance (PHR) has been observed in YIG/IrMn
bilayer at different temperatures, while the GGG/IrMn (GGG= Gd3Ga5O12) shows
constant PHR for different magnetic field angles at both 10 K and 300 K. This
provides evidence that IrMn has interfacial spins which can be led by FM in
YIG/IrMn structure. A hysteresis can be observed in PHR-magnetic field angle
loop of YIG/IrMn films at 10 K, indicating the irreversible switching of IrMn
interfacial spins at low temperature.",1410.1112v1
2016-11-25,Electrical Detection of Spin Backflow from an Antiferromagnetic Insulator/Y3Fe5O12 Interface,"Spin Hall magnetoresistance (SMR) has been observed in Pt/NiO/Y3Fe5O12 (YIG)
heterostructures with characteristics very different from those in Pt/YIG. We
show that the SMR in Pt/NiO/YIG strongly correlates with spin conductance, both
sharing very strong temperature dependence due to antiferromagnetic magnons and
spin fluctuation. This phenomenon indicates that spin current generated by spin
Hall effect in the Pt transmits through the insulating NiO and is reflected
from the NiO/YIG interface. Inverted SMR has been observed below a temperature
which increases with the NiO thickness, suggesting spin-flip reflection from
the antiferromagnetic NiO exchange coupled with the YIG.",1611.08593v1
2017-05-05,Thermographic measurements of the spin Peltier effect in metal/yttrium-iron-garnet junction systems,"The spin Peltier effect (SPE), heat-current generation due to spin-current
injection, in various metal (Pt, W, and Au single layers and Pt/Cu
bilayer)/ferrimagnetic insulator (yttrium iron garnet: YIG) junction systems
has been investigated by means of a lock-in thermography (LIT) method. The SPE
is excited by a spin current across the metal/YIG interface, which is generated
by applying a charge current to the metallic layer via the spin Hall effect.
The LIT method enables the thermal imaging of the SPE free from the
Joule-heating contribution. Importantly, we observed spin-current-induced
temperature modulation not only in the Pt/YIG and W/YIG systems but also in the
Au/YIG and Pt/Cu/YIG systems, excluding the possible contamination by anomalous
Ettingshausen effects due to proximity-induced ferromagnetism near the
metal/YIG interface. As demonstrated in our previous study, the SPE signals are
confined only in the vicinity of the metal/YIG interface; we buttress this
conclusion by reducing a spatial blur due to thermal diffusion in an infrared
emission layer on the sample surface used for the LIT measurements. We also
found that the YIG-thickness dependence of the SPE is similar to that of the
spin Seebeck effect measured in the same Pt/YIG sample, implying the reciprocal
relation between them.",1705.02094v1
2017-12-21,Exchange-torque-induced excitation of perpendicular standing spin waves in nanometer-thick YIG films,"Spin waves in ferrimagnetic yttrium iron garnet (YIG) films with ultralow
magnetic damping are relevant for magnon-based spintronics and low-power
wave-like computing. The excitation frequency of spin waves in YIG is rather
low in weak external magnetic fields because of its small saturation
magnetization, which limits the potential of YIG films for high-frequency
applications. Here, we demonstrate how exchange-coupling to a CoFeB film
enables efficient excitation of high-frequency perpendicular standing spin
waves (PSSWs) in nanometer-thick (80 nm and 295 nm) YIG films using uniform
microwave magnetic fields. In the 295-nm-thick YIG film, we measure intense
PSSW modes up to 10th order. Strong hybridization between the PSSW modes and
the ferromagnetic resonance mode of CoFeB leads to characteristic anti-crossing
behavior in broadband spin-wave spectra. A dynamic exchange torque at the
YIG/CoFeB interface explains the excitation of PSSWs. The localized torque
originates from exchange coupling between two dissimilar magnetization
precessions in the YIG and CoFeB layers. As a consequence, spin waves are
emitted from the YIG/CoFeB interface and PSSWs form when their wave vector
matches the perpendicular confinement condition. PSSWs are not excited when the
exchange coupling between YIG and CoFeB is suppressed by a Ta spacer layer.
Micromagnetic simulations confirm the exchange-torque mechanism.",1712.08204v1
2013-04-08,YIG thickness and frequency dependence of the spin-charge current conversion in YIG/Pt systems,"We report the frequency dependence of the spin current emission in a hybrid
ferrimagnetic insulator/normal metal system as function of the insulating layer
thickness. The system is based on a yttrium iron garnet (YIG) film [0.2, 1, and
3 \mu m] grown by liquid-phase-epitaxy coupled with a spin current detector of
platinum [6 nm]. A strong YIG thickness dependence of the efficiency of the
spin pumping has been observed. The highest conversion factor \Delta V/P_{abs}
has been demonstrated for the thinner YIG (1.79 and 0.55 mV/mW^{-1} at 2.5 and
10 GHz, respectively) which presents an interest for the realisation of
YIG-based devices. A strong YIG thickness dependence of the efficiency of the
spin pumping has been also observed and we demonstrate the threshold frequency
dependence of the three-magnon splitting process.",1304.2190v1
2016-04-28,Platinum/Yttrium Iron Garnet Inverted Structures for Spin Current Transport,"30-80 nm thick yttrium iron garnet (YIG) films are grown by pulsed laser
deposition on a 5 nm thick sputtered Pt atop gadolinium gallium garnet
substrate (GGG) (110). Upon post-growth rapid thermal annealing, single crystal
YIG(110) emerges as if it were epitaxially grown on GGG(110) despite the
presence of the intermediate Pt film. The YIG surface shows atomic steps with
the root-mean-square roughness of 0.12 nm on flat terraces. Both Pt/YIG and
GGG/Pt interfaces are atomically sharp. The resulting YIG(110) films show clear
in-plane uniaxial magnetic anisotropy with a well-defined easy axis along <001>
and a peak-to-peak ferromagnetic resonance linewidth of 7.5 Oe at 9.32 GHz,
similar to YIG epitaxilly grown on GGG. Both spin Hall magnetoresistance and
longitudinal spin Seebeck effects in the inverted bilayers indicate excellent
Pt/YIG interface quality.",1604.08465v1
2018-10-17,Perpendicularly magnetized YIG films with small Gilbert damping constant and anomalous spin transport properties,"The Y3Fe5O12 (YIG) films with perpendicular magnetic anisotropy (PMA) have
recently attracted a great deal of attention for spintronics applications.
Here, we report the induced PMA in the ultrathin YIG films grown on
(Gd2.6Ca0.4)(Ga4.1Mg0.25Zr0.65)O12 (SGGG) substrates by epitaxial strain
without preprocessing. Reciprocal space mapping shows that the films are
lattice-matched to the substrates without strain relaxation. Through
ferromagnetic resonance and polarized neutron reflectometry measurements, we
find that these YIG films have ultra-low Gilbert damping constant with a
magnetic dead layer as thin as about 0.3 nm at the YIG/SGGG interfaces.
Moreover, the transport behavior of the Pt/YIG/SGGG films reveals an
enhancement of spin mixing conductance and a large non-monotonic magnetic field
dependence of anomalous Hall effect as compared with the Pt/YIG/Gd3Ga5O12 (GGG)
films. The non-monotonic anomalous Hall signal is extracted in the temperature
range from 150 to 350 K, which has been ascribed to the possible non-collinear
magnetic order at the Pt/YIG interface induced by uniaxial strain.",1810.07384v2
2023-06-24,Magnon confinement in an all-on-chip YIG cavity resonator using hybrid YIG/Py magnon barriers,"Confining magnons in cavities can introduce new functionalities to magnonic
devices, enabling future magnonic structures to emulate established photonic
and electronic components. As a proof-of-concept, we report magnon confinement
in a lithographically defined all-on-chip YIG cavity created between two
YIG/Permalloy bilayers. We take advantage of the modified magnetic properties
of covered/uncovered YIG film to define on-chip distinct regions with
boundaries capable of confining magnons. We confirm this by measuring multiple
spin pumping voltage peaks in a 400 nm wide platinum strip placed along the
center of the cavity. These peaks coincide with multiple spin-wave resonance
modes calculated for a YIG slab with the corresponding geometry. The
fabrication of micrometer-sized YIG cavities following this technique
represents a new approach to control coherent magnons, while the spin pumping
voltage in a nanometer-sized Pt strip demonstrates to be a non-invasive local
detector of the magnon resonance intensity.",2306.14029v2
2023-09-21,Single-crystalline YIG nanoflakes with uniaxial in-plane anisotropy and diverse crystallographic orientations,"We study Y3Fe5O12 (YIG) nanoflakes that we produce via mechanical cleaving
and exfoliation of YIG single crystals. By characterizing their structural and
magnetic properties, we find that these YIG nanoflakes have surfaces oriented
along unusual crystallographic axes and uniaxial in-plane magnetic anisotropy
due to their shape, both of which are not commonly available in YIG thin films.
These physical properties, combined with the possibility of picking up the YIG
nanoflakes and stacking them onto nanoflakes of other van der Waals materials
or pre-patterned electrodes or waveguides, open unexplored possibilities for
magnonics and for the realization of novel YIG-based heterostructures and
devices.",2309.12477v1
2018-11-29,"High Saturation Magnetization, Low Coercivity and Fine YIG Nanoparticles Prepared by Modifying Co-Precipitation Method","Nanoparticles with their specific properties newly have drawn a great deal of
attention of researchers [1-3]Yttrium iron Garnet magnetic nanoparticles
(YIG-NPs) are promising materials with novel applications in microwave,
spintronics, magnonics, and magneto-optical devices. However, achieving stable
and remarkable magnetic YIG-NPs has been remaining as a great challenge. In
this paper, synthesized YIG-NPs by modifying co-precipitation (MCP) method is
reported. Structural and magnetic properties of final products are compared to
those of the materials prepared by citrate-nitrate (CN) method. Smaller
crystals and particle size have been found by MCP method comparing to that of
synthesized by CN method. Using a relatively low annealing temperatures for
both sets of samples (~700 {\deg}C), the final YIG samples prepared by MCP
method show more structural purity than those made by CN method. Higher
saturation magnetization (Ms) and lower coercivity (Hc) are observed in MCP YIG
sample (23.23 emu/g 36 and 30.1 Oe) than the CN prepared YIG sample (16.43
emu/g and 44.95 Oe). The Curie temperature is measured to be 569 {\deg}C for
the MCP YIG sample determined from set of Ms measurement at different
temperatures ranging from 80-600 K. These findings lead to significant
improvement in quality of synthesized (synthetic methods) of YIG-NPs.",1811.12511v1
2018-11-29,Structural and Magnetic Study of Metallo-Organic YIG Powder Using 2-ethylhexanoate Carboxylate Based Precursors,"The crystallization and magnetic behavior of yttrium iron garnet (YIG)
prepared by metallo-organic decomposition (MOD) method are discussed. The
chemistry and physics related to synthesis of iron and yttrium carboxylates
based on 2-ethylhexanoic acid (2EHA) are studied, since no literature was found
which elucidates synthesis of metallo-organic precursor of YIG in spite of the
literatures of doped YIG samples such as Bi-YIG. Typically, the metal
carboxylates used in preparation of ceramic oxide materials are
2-ethylhexanoate (2EH) solvents. Herein, the synthesis, thermal behavior and
solubility of yttrium and iron 2EH used in synthesis of YIG powder by MOD are
reported. The crystallization and magnetic parameters, including saturation
magnetization and coercivity of these samples, smoothly change as a function of
the annealing temperature. It is observed that high sintering temperature of
1300 to 1400 {\deg}C promotes the diffraction peaks of YIG, therefore, we can
conclude that the formation of YIG in MOD method increases the crystallization
temperature. The maximum value of saturation magnetization and minimum value of
coercivity and remanence are observed for the sample sintered at 1200{\deg}C
which are 13.7 emu/g, 10.38 Oe and 1.5 emu/g, respectively. This study cites
the drawbacks in chemical synthesis of metallo-organic based YIG production.",1811.12514v1
2013-09-09,Induced magneto-transport properties at palladium/yttrium iron garnet interface,"As a thin layer of palladium (Pd) is directly deposited on an yttrium iron
garnet or YIG (Y3Fe5O12) magnetic insulator film, Pd develops both low- and
high-field magneto-transport effects that are absent in standalone Pd or thick
Pd on YIG. While the low-field magnetoresistance peak of Pd tracks the coercive
field of the YIG film, the much larger high-field magnetoresistance and the
Hall effect do not show any obvious relationship with the bulk YIG
magnetization. The distinct high-field magneto-transport effects in Pd are
shown to be caused by interfacial local moments in Pd.",1309.2213v1
2015-09-14,Spin Transport in Antiferromagnetic Insulators Mediated by Magnetic Correlations,"We report a systematic study of spin transport in antiferromagnetic (AF)
insulators having a wide range of ordering temperatures. Spin current is
dynamically injected from Y3Fe5O12 (YIG) into various AF insulators in
Pt/insulator/YIG trilayers. Robust, long-distance spin transport in the AF
insulators is observed, which shows strong correlation with the AF ordering
temperatures. We find a striking linear relationship between the spin decay
length in the AFs and the damping enhancement in YIG, suggesting the critical
role of magnetic correlations in the AF insulators as well as at the AF/YIG
interfaces for spin transport in magnetic insulators.",1509.04336v1
2016-03-11,Investigation of anomalous-Hall and spin-Hall effects of antiferromagnetic IrMn sandwiched by Pt and YIG layers,"We report an investigation of temperature and IrMn layered thickness
dependence of anomalous-Hall resistance (AHR), anisotropic magnetoresistance
(AMR), and magnetization on Pt/Ir20Mn80/Y3Fe5O12 (Pt/IrMn/YIG)
heterostructures. The magnitude of AHR is dramatically enhanced compared with
Pt/YIG bilayers. The enhancement is much more profound at higher temperatures
and peaks at the IrMn thickness of 3 nm. The observed spin-Hall
magnetoresistance (SMR) in the temperature range of 10-300 K indicates that the
spin current generated in the Pt layer can penetrate the entire thickness of
the IrMn layer to interact with the YIG layer. The lack of conventional
anisotropic magnetoresistance (CAMR) implies that the insertion of the IrMn
layer between Pt and YIG efficiently suppresses the magnetic proximity effect
(MPE) on induced Pt moments by YIG. Our results suggest that the dual roles of
the InMn insertion in Pt/IrMn/YIG heterostructures are to block the MPE and to
transport the spin current between Pt and YIG layers. We discuss possible
mechanisms for the enhanced AHR.",1603.03578v2
2020-11-15,A tunable magneto-acoustic oscillator with low phase noise,"A frequency-tunable low phase noise magneto-acoustic resonator is developed
on the base of a parallel-plate straight-edge bilayer consisting of a
yttrium-iron garnet (YIG) layer grown on a substrate of a gallium-gadolinium
garnet(GGG). When a YIG/GGG sample forms an ideal parallel plate, it supports a
series of high-quality-factor acoustic modes standing along the plate
thickness. Due to the magnetostriction of the YIG layer the ferromagnetic
resonance (FMR) mode of the YIG layer can strongly interact with the acoustic
thickness modes of the YIG/GGG structure, when the modes' frequencies match. A
particular acoustic thickness mode used for the resonance excitations of the
hybrid magneto-acoustic oscillations in a YIG/GGG bilayer is chosen by the YIG
layer FMR frequency, which can be tuned by the variation of the external bias
magnetic field. A composite magneto-acoustic oscillator, which includes an
FMR-based resonance pre-selector, is developed to guarantee satisfaction of the
Barkhausen criteria for a single-acoustic-mode oscillation regime. The
developed low phase noise composite magneto-acoustic oscillator can be tuned
from 0.84 GHz to 1 GHz with an increment of about 4.8 MHz (frequency distance
between the adjacent acoustic thickness modes in a YIG/GGG parallel plate), and
demonstrates the phase noise of -116 dBc/Hz at the offset frequency of 10 kHz.",2011.07648v1
2021-09-13,Control of magnetization dynamics by substrate orientation in YIG thin films,"Yttrium Iron Garnet (YIG) and bismuth (Bi) substituted YIG (Bi0.1Y2.9Fe5O12,
BYG) films are grown in-situ on single crystalline Gadolinium Gallium Garnet
(GGG) substrates [with (100) and (111) orientations] using pulsed laser
deposition (PLD) technique. As the orientation of the Bi-YIG film changes from
(100) to (111), the lattice constant is enhanced from 12.384 {\AA} to 12.401
{\AA} due to orientation dependent distribution of Bi3+ ions at dodecahedral
sites in the lattice cell. Atomic force microscopy (AFM) images show smooth
film surfaces with roughness 0.308 nm in Bi-YIG (111). The change in substrate
orientation leads to the modification of Gilbert damping which, in turn, gives
rise to the enhancement of ferromagnetic resonance (FMR) line width. The best
values of Gilbert damping are found to be (0.54)*10-4, for YIG (100) and
(6.27)*10-4, for Bi-YIG (111) oriented films. Angle variation measurements of
the Hr are also performed, that shows a four-fold symmetry for the resonance
field in the (100) grown film. In addition, the value of effective
magnetization (4{\pi}Meff) and extrinsic linewidth ({\Delta}H0) are observed to
be dependent on substrate orientation. Hence PLD growth can assist
single-crystalline YIG and BYG films with a perfect interface that can be used
for spintronics and related device applications.",2109.05901v1
2014-08-13,Quantitative Temperature Dependence of Longitudinal Spin Seebeck Effect at High Temperatures,"This article reports temperature-dependent measurements of longitudinal spin
Seebeck effects (LSSEs) in Pt/Y$_3$Fe$_5$O$_{12}$ (YIG)/Pt systems in a high
temperature range from room temperature to above the Curie temperature of YIG.
The experimental results show that the magnitude of the LSSE voltage in the
Pt/YIG/Pt systems rapidly decreases with increasing the temperature and
disappears above the Curie temperature. The critical exponent of the LSSE
voltage in the Pt/YIG/Pt systems at the Curie temperature was estimated to be
3, which is much greater than that for the magnetization curve of YIG. This
difference highlights the fact that the mechanism of the LSSE cannot be
explained in terms of simple static magnetic properties in YIG.",1408.2972v2
2016-04-24,Who pumps spin current into nonmagnetic-metal (NM) layer in YIG/NM multilayers at ferromagnetic resonance?,"Spin pumping in Yttrium-iron-garnet (YIG)/nonmagnetic-metal (NM) layer
systems under ferromagnetic resonance (FMR) conditions is a popular method of
generating spin current in the NM layer. A good understanding of the spin
current source is essential in extracting spin Hall angle of the NM and in
potential spintronics applications. It is widely believed that spin current is
pumped from precessing YIG magnetization into NM layer. Here, by combining
microwave absorption and DC-voltage measurements on YIG/Pt and YIG/NM1/NM2
(NM1=Cu or Al, NM2=Pt or Ta), we unambiguously showed that spin current in NM
came from the magnetized NM surface (in contact with YIG) due to the magnetic
proximity effect (MPE), rather than the precessing YIG magnetization. This
conclusion is reached through our unique detecting method where the FMR
microwave absorption of the magnetized NM surface, hardly observed in the
conventional FMR experiments, was greatly amplified when the electrical
detection circuit was switched on.",1604.07025v1
2016-10-24,Tunable sign change of spin Hall magnetoresistance in Pt/NiO/YIG structures,"Spin Hall magnetoresistance (SMR) has been investigated in Pt/NiO/YIG
structures in a wide range of temperature and NiO thickness. The SMR shows a
negative sign below a temperature which increases with the NiO thickness. This
is contrary to a conventional SMR theory picture applied to Pt/YIG bilayer
which always predicts a positive SMR. The negative SMR is found to persist even
when NiO blocks the spin transmission between Pt and YIG, indicating it is
governed by the spin current response of NiO layer. We explain the negative SMR
by the NiO 'spin-flop' coupled with YIG, which can be overridden at higher
temperatures by positive SMR contribution from YIG. This highlights the role of
magnetic structure in antiferromagnets for transport of pure spin current in
multilayers.",1610.07362v2
2022-04-12,Spin Peltier effect and its length scale in Pt/YIG system at high temperatures,"The temperature and yttrium-iron-garnet (YIG) thickness dependences of the
spin Peltier effect (SPE) have been investigated using a Pt/YIG junction system
at temperatures ranging from room temperature to the Curie temperature of YIG
by the lock-in thermography method. By analyzing the YIG thickness dependence
using an exponential decay model, the characteristic length of SPE in YIG is
estimated to be 0.9 $\mu$m near room temperature and almost constant even near
the Curie temperature. The high-temperature behavior of SPE is clearly
different from that of the spin Seebeck effect, providing a clue for
microscopically understanding the reciprocal relation between them.",2204.05482v1
2015-03-20,Control of spin current by a magnetic YIG substrate in NiFe/Al nonlocal spin valves,"We study the effect of a magnetic insulator (Yttrium Iron Garnet - YIG)
substrate on the spin transport properties of Ni$_{80}$Fe$_{20}$/Al nonlocal
spin valve (NLSV) devices. The NLSV signal on the YIG substrate is about 2 to 3
times lower than that on a non magnetic SiO$_2$ substrate, indicating that a
significant fraction of the spin-current is absorbed at the Al/YIG interface.
By measuring the NLSV signal for varying injector-to-detector distance and
using a three dimensional spin-transport model that takes spin current
absorption at the Al/YIG interface into account we obtain an effective
spin-mixing conductance $G_{\uparrow\downarrow}\simeq 5 - 8\times
10^{13}~\Omega^{-1}$m$^{-2}$. We also observe a small but clear modulation of
the NLSV signal when rotating the YIG magnetization direction with respect to
the fixed spin polarization of the spin accumulation in the Al. Spin relaxation
due to thermal magnons or roughness of the YIG surface may be responsible for
the observed small modulation of the NLSV signal.",1503.06108v1
2017-11-21,Ionic Modulation of Interfacial Magnetism through Electrostatic Doping in Pt/YIG bilayer heterostructure,"Voltage modulation of yttrium iron garnet (YIG) with compactness, high speed
response, energy efficiency and both practical/theoretical siginificances can
be widely applied to various YIG based spintronics such as spin Hall, spin
pumping, spin Seeback effects. Here we initial an ionic modulation of
interfacial magnetism process on YIG/Pt bilayer heterostructures, where the Pt
capping would influence the ferromagnetic (FMR) field position significantly,
and realize a significant magnetism enhancement in bilayer system. A large
voltage induced FMR field shifts of 690 Oe has been achieved in YIG (13 nm)/Pt
(3 nm) multilayer heterostructures under a small voltage bias of 4.5 V. The
remarkable ME tunability comes from voltage induced extra FM ordering in Pt
metal layer near the Pt/YIG interface. The first-principle theoretical
simulation reveal that the electrostatic doping induced Pt5+ ions have strong
magnetic ordering due to uncompensated d orbit electrons. The large voltage
control of FMR change pave a foundation towards novel voltage tunable YIG based
spintronics.",1711.07610v3
2018-04-19,Effect of magnons on interfacial phonon drag in YIG/metal systems,"We examine substrate-to-film interfacial phonon drag on typical spin Seebeck
heterostructures, in particular studying the effect of ferromagnetic magnons on
the phonon-electron drag dynamics at the interface. We investigate with high
precision the effect of magnons in the Pt|YIG heterostructure by designing a
magnon drag thermocouple; a hybrid sample with both a Pt|YIG film and Pt|GGG
interface accessible isothermally via a 6 nm Pt film patterned in a rectangular
U shape with one arm on the 250 nm YIG film and the other on GGG. We measure
the voltage between the isothermal ends of the U, while applying a temperature
gradient parallel to the arms and perpendicular to the bottom connection. With
a uniform applied temperature gradient, the Pt acts as a differential
thermocouple. We conduct temperature-dependent longitudinal thermopower
measurements on this sample. Results show that the YIG interface actually
decreases the thermopower of the film, implying that magnons impede phonon
drag. We repeat the experiment using metals with low spin Hall angles, Ag and
Al, in place of Pt. We find that the phonon drag peak in thermopower is killed
in samples where the metallic interface is with YIG. We also investigate
magneto-thermopower and YIG film thickness dependence. These measurements
confirm our findings that magnons impede the phonon-electron drag interaction
at the metallic interface in these heterostructures.",1804.07023v1
2018-10-16,Spin-wave-induced lateral temperature gradient in a YIG thin film/GGG system excited in an ESR cavity,"Lateral thermal gradient of an yttrium iron garnet (YIG) film under the
microwave application in the cavity of the electron spin resonance system (ESR)
was measured at room temperature by fabricating a Cu/Sb thermocouple onto it.
To date, thermal transport in YIG films caused by the Damon-Eshbach mode (DEM)
- the unidirectional spin-wave heat conveyer effect - was demonstrated only by
the excitation using coplanar waveguides. Here we show that effect exists even
under YIG excitation using the ESR cavity - tool often employed to realize spin
pumping. The temperature difference observed around the ferromagnetic resonance
(FMR) field under the 4 mW microwave power peaked at 13 mK. The observed
thermoelectric signal indicates the imbalance of the population between the
DEMs that propagate near the top and bottom surfaces of the YIG film. We
attribute the DEM population imbalance to the different magnetic damping near
the top and bottom YIG surfaces. Additionally, the spin wave dynamics of the
system were investigated using the micromagnetic simulations. The micromagnetic
simulations confirmed the existence of the DEM imbalance in the system with the
increased Gilbert damping at one of the YIG interfaces. The reported results
are indispensable for the quantitative estimation of the electromotive force in
the spin-charge conversion experiments using ESR cavities.",1810.06875v1
2021-12-21,Fast long-wavelength exchange spin waves in partially-compensated Ga:YIG,"Spin waves in yttrium iron garnet (YIG) nano-structures attract increasing
attention from the perspective of novel magnon-based data processing
applications. For short wavelengths needed in small-scale devices, the group
velocity is directly proportional to the spin-wave exchange stiffness constant
$\lambda_\mathrm{ex}$. Using wave vector resolved Brillouin Light Scattering
(BLS) spectroscopy, we directly measure $\lambda_\mathrm{ex}$ in Ga-substituted
YIG thin films and show that it is about three times larger than for pure YIG.
Consequently, the spin-wave group velocity overcomes the one in pure YIG for
wavenumbers $k > 4$ rad/$\mu$m, and the ratio between the velocities reaches a
constant value of around 3.4 for all $k > 20$ rad/$\mu$m. As revealed by
vibrating-sample magnetometry (VSM) and ferromagnetic resonance (FMR)
spectroscopy, Ga:YIG films with thicknesses down to 59 nm have a low Gilbert
damping ($\alpha < 10^{-3}$), a decreased saturation magnetization $\mu_0
M_\mathrm{S}~\approx~20~$mT and a pronounced out-of-plane uniaxial anisotropy
of about $\mu_0 H_{\textrm{u1}} \approx 95 $ mT which leads to an out-of-plane
easy axis. Thus, Ga:YIG opens access to fast and isotropic spin-wave transport
for all wavelengths in nano-scale systems independently of dipolar effects.",2112.11348v1
2011-08-22,Acoustic spin pumping: Direct generation of spin currents from sound waves in Pt/Y3Fe5O12 hybrid structures,"Using a Pt/Y3Fe5O12 (YIG) hybrid structure attached to a piezoelectric
actuator, we demonstrate the generation of spin currents from sound waves. This
""acoustic spin pumping"" (ASP) is caused by the sound wave generated by the
piezoelectric actuator, which then modulates the distribution function of
magnons in the YIG layer and results in a pure-spin-current injection into the
Pt layer across the Pt/YIG interface. In the Pt layer, this injected spin
current is converted into an electric voltage due to the inverse spin-Hall
effect (ISHE). The ISHE voltage induced by the ASP is detected by measuring
voltage in the Pt layer at the piezoelectric resonance frequency of the
actuator coupled with the Pt/YIG system. The frequency-dependent measurements
enable us to separate the ASP-induced signals from extrinsic heating effects.
Our model calculation based on the linear response theory provides us with a
qualitative and quantitative understanding of the ASP in the Pt/YIG system.",1108.4238v1
2015-01-12,Anomalous Hall effect in YIG$|$Pt bilayers,"We measure the ordinary and the anomalous Hall effect in a set of yttrium
iron garnet$|$platinum (YIG$|$Pt) bilayers via magnetization orientation
dependent magnetoresistance experiments. Our data show that the presence of the
ferrimagnetic insulator YIG leads to an anomalous Hall like signature in Pt,
sensitive to both Pt thickness and temperature. Interpretation of the
experimental findings in terms of the spin Hall anomalous Hall effect indicates
that the imaginary part of the spin mixing interface conductance
$G_{\mathrm{i}}$ plays a crucial role in YIG$|$Pt bilayers. In particular, our
data suggest a sign change in $G_{\mathrm{i}}$ between $10\,\mathrm{K}$ and
$300\,\mathrm{K}$. Additionally, we report a higher order Hall effect, which
appears in thin Pt films on YIG at low temperatures.",1501.02574v3
2015-03-19,Critical suppression of spin Seebeck effect by magnetic fields,"The longitudinal spin Seebeck effect (LSSE) in Pt/Y$_3$Fe$_5$O$_{12}$ (YIG)
junction systems has been investigated at various magnetic fields and
temperatures. We found that the LSSE voltage in a Pt/YIG-slab system is
suppressed by applying high magnetic fields and this suppression is critically
enhanced at low temperatures. The field-induced suppression of the LSSE in the
Pt/YIG-slab system is too large at around room temperature to be explained
simply by considering the effect of the Zeeman gap in magnon excitation. This
result requires us to introduce magnon-frequency-dependent mechanism into the
scenario of LSSE; low-frequency magnons dominantly contribute to the LSSE. The
magnetic field dependence of the LSSE voltage was observed to change by
changing the thickness of YIG, suggesting that the thermo-spin conversion by
the low-frequency magnons is suppressed in thin YIG films due to the long
characteristic lengths of such magnons.",1503.05764v2
2015-10-30,Pure spin-Hall magnetoresistance in Rh/Y3Fe5O12 hybrid,"We report an investigation of anisotropic magnetoresistance (AMR) and
anomalous Hall resistance (AHR) of Rh and Pt thin films sputtered on epitaxial
Y$_3$Fe$_5$O$_{12}$ (YIG) ferromagnetic insulator films. For the Pt/YIG hybrid,
large spin-Hall magnetoresistance (SMR) along with a sizable conventional
anisotropic magnetoresistance (CAMR) and a nontrivial temperature dependence of
AHR were observed in the temperature range of 5-300 K. In contrast, a reduced
SMR with negligible CAMR and AHR was found in Rh/YIG hybrid. Since CAMR and AHR
are characteristics for all ferromagnetic metals, our results suggest that the
Pt is likely magnetized by YIG due to the magnetic proximity effect (MPE) while
Rh remains free of MPE. Thus the Rh/YIG hybrid could be an ideal model system
to explore physics and devices associated with pure spin current.",1510.09007v1
2016-03-30,Low-damping transmission of spin waves through YIG/Pt-based layered structures for spin-orbit-torque applications,"We show that in YIG-Pt bi-layers, which are widely used in experiments on the
spin transfer torque and spin Hall effects, the spin-wave amplitude
significantly decreases in comparison to a single YIG film due to the
excitation of microwave eddy currents in a Pt coat. By introducing a novel
excitation geometry, where the Pt layer faces the ground plane of a microstrip
line structure, we suppressed the excitation of the eddy currents in the Pt
layer and, thus, achieved a large increase in the transmission of the
Damon-Eshbach surface spin wave. At the same time, no visible influence of an
external dc current applied to the Pt layer on the spin-wave amplitude in the
YIG-Pt bi-layer was observed in our experiments with YIG films of micrometer
thickness.",1603.09201v1
2016-08-03,Influence of yttrium iron garnet thickness and heater opacity on the nonlocal transport of electrically and thermally excited magnons,"We studied the nonlocal transport behavior of both electrically and thermally
excited magnons in yttrium iron garnet (YIG) as a function of its thickness.
For electrically injected magnons, the nonlocal signals decrease monotonically
as the YIG thickness increases. For the nonlocal behavior of the thermally
generated magnons, or the nonlocal spin Seebeck effect (SSE), we observed a
sign reversal which occurs at a certain heater-detector distance, and it is
influenced by both the opacity of the YIG/heater interface and the YIG
thickness. Our nonlocal SSE results can be qualitatively explained by the
bulk-driven SSE mechanism together with the magnon diffusion model. Using a
two-dimensional finite element model (2D-FEM), we estimated the bulk spin
Seebeck coefficient of YIG at room temperature. The quantitative disagreement
between the experimental and modeled results indicates more complex processes
going on in addition to magnon diffusion and relaxation, especially close to
the contacts.",1608.01178v1
2017-02-22,Is spin superfluidity possible in YIG films?,"Recently it was suggested that stationary spin supercurrents (spin
superfluidity) are possible in the magnon condensate observed in
yttrium-iron-garnet (YIG) magnetic films under strong external pumping. Here we
analyze this suggestion. From topology of the equilibrium order parameter in
YIG one must not expect energetic barriers making spin supercurrents
metastable. However some small barriers of dynamical origin are possible
nevertheless. The critical phase gradient (analog of the Landau critical
velocity in superfluids) is proportional to intensity of the coherent spin wave
(number of condensed magnons). The conclusion is that although spin
superfluidity in YIG films is possible in principle, the published claim of its
observation is not justified.
  The analysis revealed that the widely accepted spin-wave spectrum in YIG
films with magnetostatic and exchange interaction required revision. This led
to revision of non-linear corrections, which determine stability of the magnon
condensate with and without spin supercurrents.",1702.06994v2
2017-06-23,Detection of induced paramagnetic moments in Pt on Y$_3$Fe$_5$O$_{12}$ via x-ray magnetic circular dichroism,"Magnetic moments in an ultra-thin Pt film on a ferrimagnetic insulator
Y$_3$Fe$_5$O$_{12}$ (YIG) have been investigated at high magnetic fields and
low temperatures by means of X-ray magnetic circular dichroism (XMCD). We
observed an XMCD signal due to the magnetic moments in a Pt film at the Pt
$L_{3}$- and $L_{2}$-edges. By means of the element-specific magnetometry, we
found that the XMCD signal at the Pt $L_{3}$-edge gradually increases with
increasing the magnetic field even when the field is much greater than the
saturation field of YIG. Importantly, the observed XMCD intensity was found to
be much greater than the intensity expected from the Pauli paramagnetism of Pt
when the Pt film is attached to YIG. These results imply the emergence of
induced paramagnetic moments in Pt on YIG and explain the characteristics of
the unconventional Hall effect in Pt/YIG systems.",1706.07559v1
2017-12-07,Spin waves in coupled YIG/Co heterostructures,"We investigate yttrium iron garnet (YIG)/cobalt (Co) heterostructures using
broadband ferromagnetic resonance (FMR). We observe an efficient excitation of
perpendicular standing spin waves (PSSWs) in the YIG layer when the resonance
frequencies of the YIG PSSWs and the Co FMR line coincide. Avoided crossings of
YIG PSSWs and the Co FMR line are found and modeled using mutual spin pumping
and exchange torques. The excitation of PSSWs is suppressed by a thin aluminum
oxide (AlOx) interlayer but persists with a copper (Cu) interlayer, in
agreement with the proposed model.",1712.02561v1
2018-11-04,Role of gallium diffusion in the formation of a magnetically dead layer at Y3Fe5O12 / Gd3Ga5O12 epitaxial interface,"We have clarified the origin of magnetically dead interface layer formed in
yttrium iron garnet (YIG) films grown at above 700{\deg}C onto gadolinium
gallium garnet (GGG) substrate by means of laser molecular beam epitaxy. The
diffusion-assisted formation of a Ga-rich region at the YIG / GGG interface is
demonstrated by means of composition depth profiling performed by X-ray
photoelectron spectroscopy, secondary ion mass spectroscopy and X-ray and
neutron reflectometry. Our finding is in sharp contrast to the earlier
expressed assumption that Gd acts as a migrant element in the YIG/GGG system.
We further correlate the presence of Ga-rich transition layer with considerable
quenching of ferromagnetic resonance and spin wave propagation in thin YIG
films. Finally, we clarify the origin of the enigmatic low-density overlayer
that is often observed in neutron and X-ray reflectometry studies of the YIG /
GGG epitaxial system.",1811.01321v2
2018-11-13,Experimental proof of the reciprocal relation between spin Peltier and spin Seebeck effects in a bulk YIG/Pt bilayer,"We verify for the first time the reciprocal relation between the spin Peltier
and spin Seebeck effects in a bulk YIG/Pt bilayer. Both experiments are
performed on the same YIG/Pt device by a setup able to accurately determine
heat currents and to separate the spin Peltier heat from the Joule heat
background. The sample-specific value for the characteristics of both effects
measured on the present YIG/Pt bilayer is $(6.2 \pm 0.4)\times 10^{-3} \,\,
\mbox{KA$^{-1}$}$. In the paper we also discuss the relation of both effects
with the intrinsic and extrinsic parameters of YIG and Pt and we envisage
possible strategies to optimize spin Peltier refrigeration.",1811.05120v1
2019-03-06,Microwave magnon damping in YIG films at millikelvin temperatures,"Magnon systems used in quantum devices require low damping if coherence is to
be maintained. The ferrimagnetic electrical insulator yttrium iron garnet (YIG)
has low magnon damping at room temperature and is a strong candidate to host
microwave magnon excitations in future quantum devices. Monocrystalline YIG
films are typically grown on gadolinium gallium garnet (GGG) substrates. In
this work, comparative experiments made on YIG waveguides with and without GGG
substrates indicate that the material plays a significant role in increasing
the damping at low temperatures. Measurements reveal that damping due to
temperature-peak processes is dominant above 1 K. Damping behaviour that we
show can be attributed to coupling to two-level fluctuators (TLFs) is observed
below 1 K. Upon saturating the TLFs in the substrate-free YIG at 20 mK,
linewidths of 1.4 MHz are achievable: lower than those measured at room
temperature.",1903.02527v3
2019-03-28,Acoustic excitation and electrical detection of spin waves and spin currents in hypersonic bulk waves resonator with YIG/Pt system,"We report on the self-consisted semi-analytical theory of magnetoelastic
excitation and electrical detection of spin waves and spin currents in
hypersonic bulk acoustic waves resonator with ZnO-GGG-YIG/Pt layered structure.
Electrical detection of acoustically driven spin waves occurs due to spin
pumping from YIG to Pt and inverse spin Hall (ISHE) effect in Pt as well as due
to electrical response of ZnO piezotransducer. The frequency-field dependences
of the resonator frequencies and ISHE voltage $U_{ISHE}$ are correlated with
experimental ones observed previously. Their fitting allows to determine some
magnetic and magnetoelastic parameters of YIG. The analysis of the YIG film
thickness influence on $U_{ISHE}$ gives the possibility to find the optimal
thickness for maximal $U_{ISHE}$ value.",1903.12130v2
2019-06-04,Thickness dependence of spin Peltier effect visualized by thermal imaging technique,"Magnon propagation length in a ferrimagnetic insulator yttrium iron garnet
(YIG) has been investigated by measuring and analyzing the YIG-thickness t_YIG
dependence of the spin Peltier effect (SPE) in a Pt/YIG junction system. By
means of the lock-in thermography technique, we measured the spatial
distribution of the SPE-induced temperature modulation in the Pt/YIG system
with the t_YIG gradation, allowing us to obtain the accurate t_YIG dependence
of SPE with high t_YIG resolution. Based on the t_YIG dependence of SPE, we
verified the applicability of several phenomenological models to estimate the
magnon diffusion length in YIG.",1906.01560v3
2020-10-24,Octave-Tunable Magnetostatic Wave YIG Resonators on a Chip,"We have designed, fabricated, and characterized magnetostatic wave (MSW)
resonators on a chip. The resonators are fabricated by patterning
single-crystal yttrium iron garnet (YIG) film on a gadolinium gallium garnet
(GGG) substrate and excited by loop-inductor transducers. We achieved this
technology breakthrough by developing a YIG film etching process and
fabricating thick aluminum coplanar waveguide (CPW) inductor loop around each
resonator to individually address and excite MSWs. At 4.77 GHz, the 0.68 square
mm resonator achieves a quality factor Q > 5000 with a bias field of 987 Oe. We
also demonstrate YIG resonator tuning by more than one octave from 3.63 to 7.63
GHz by applying an in-plane external magnetic field. The measured quality
factor of the resonator is consistently over 3000 above 4 GHz. The
micromachining technology enables the fabrication of multiple single- and
two-port YIG resonators on the same chip with all resonators demonstrating
octave tunability and high Q .",2010.12732v1
2021-09-24,Damping in yttrium iron garnet film with an interface,"We report strong damping enhancement in a 200 nm thick yttrium iron garnet
(YIG) film due to spin inhomogeneity at the interface. The growth-induced thin
interfacial gadolinium iron garnet (GdIG) layer antiferromagnetically (AFM)
exchange couples with the rest of the YIG layer. The out-of-plane angular
variation of ferromagnetic resonance (FMR) linewidth $\Delta H$ reflects a
large inhomogeneous distribution of effective magnetization $\Delta 4 \pi
M_{eff}$ due to the presence of an exchange springlike moments arrangement in
YIG. We probe the spin inhomogeneity at the YIG-GdIG interface by performing an
in-plane angular variation of resonance field $H_{r}$, leading to a
unidirectional feature. The large extrinsic $\Delta 4\pi M_{eff}$ contribution,
apart from the inherent intrinsic Gilbert contribution, manifests enhanced
precessional damping in YIG film.",2109.12071v1
2022-04-04,Inverse Orbital Torque via Spin-Orbital Entangled States,"While current-induced torque by orbital current has been experimentally found
in various structures, evidence for its reciprocity has been missing so far.
Here, we report experimental evidence of strong inverse orbital torque in
YIG/Pt/CuOx (YIG = Y3Fe5O12) mediated by spin-orbital entangled electronic
states in Pt. By injecting spin current from YIG to Pt by the spin pumping via
ferromagnetic resonance and by the spin Seebeck effect, we find a pronounced
inverse spin Hall effect-like signal. While a part of the signal is explained
as due to the inverse spin-orbital Hall effect in Pt, we also find substantial
increase of the signal in YIG/Pt/CuOx structures compared to the signal in
YIG/Pt. We attribute this to the inverse orbital Rashba-Edelstein effect at
Pt/CuOx interface mediated by the spin-orbital entangled states in Pt. Our work
paves the way toward understanding of spin-orbital entangled physics in
nonequilibrium and provides a way for electrical detection of the orbital
current in orbitronic device applications.",2204.01825v2
2024-02-22,Unraveling the origin of antiferromagnetic coupling at YIG/permalloy interface,"We investigate the structural and electronic origin of antiferromagnetic
coupling in the Yttrium iron garnet (YIG) and permalloy (Py) bilayer system at
the atomic level. Ferromagnetic Resonance (FMR) reveal unique hybrid modes in
samples prepared with surface ion milling, indicative of antiferromagnetic
exchange coupling at the YIG/Py interface. Using scanning transmission electron
microscopy (STEM), we highlight significant interfacial differences introduced
by ion-milling. The observations suggests that the antiferromagnetic coupling
in YIG/Py bilayers is predominantly driven by an oxygen-mediated super-exchange
coupling mechanism on the tetrahedral Fe terminated YIG surface, which is
supported by density functional theory (DFT) calculations. This research
provides critical insight into the fundamental mechanisms governing the
efficiency of coupling in magnetic bilayers and underscores the pivotal role of
oxide surface termination in modulating magnetic interfacial dynamics.",2402.14553v2
2013-02-28,Spin mixing conductance at a well-controlled platinum/yttrium iron garnet interface,"A platinum (Pt)/yttrium iron garnet (YIG) bilayer system with a
well-controlled interface has been developed; spin mixing conductance at the
Pt/YIG interface has been studied. Crystal perfection at the interface is
experimentally demonstrated to contribute to large spin mixing conductance. The
spin mixing conductance is obtained to be $1.3\times10^{18} \rm{m^{-2}}$ at the
well-controlled Pt/YIG interface, which is close to a theoretical prediction.",1302.7091v3
2014-10-07,Influence of interface condition on spin-Seebeck effects,"The longitudinal spin-Seebeck effect (LSSE) has been investigated for
Pt/yttrium iron garnet (YIG) bilayer systems. The magnitude of the voltage
induced by the LSSE is found to be sensitive to the Pt/YIG interface condition.
We observed large LSSE voltage in a Pt/YIG system with a better crystalline
interface, while the voltage decays steeply when an amorphous layer is
introduced at the interface artificially.",1410.1655v1
2016-12-19,Thickness dependence study of current-driven ferromagnetic resonance in Y3Fe5O12/heavy metal bilayers,"We use ferromagnetic resonance to study the current-induced torques in
YIG/heavy metal bilayers. YIG samples with thickness varying from 14.8 nm to 80
nm, with Pt or Ta thin film on top, are measured by applying a microwave
current into the heavy metals and measuring the longitudinal DC voltage
generated by both spin rectification and spin pumping. From a symmetry analysis
of the FMR lineshape and its dependence on YIG thickness, we deduce that the
Oersted field dominates over spin-transfer torque in driving magnetization
dynamics.",1612.06111v1
2018-03-10,Atomic-scale structure and chemistry of YIG/GGG Interface,"Y3Fe5O12 (YIG) is a promising candidate for spin wave devices. In the thin
film devices, the interface between YIG and substrate may play important roles
in determining the device properties. Here, we use spherical
aberration-corrected scanning electron microscopy and spectroscopy to study the
atomic arrangement, chemistry and electronic structure of the YIG/Gd3Ga5O12
(GGG) interface. We find that the chemical bonding of the interface is
FeO-GdGaO and the interface remains sharp in both atomic and electronic
structures. These results provide necessary information for understanding the
properties of interface and also for atomistic calculation.",1803.03799v1
2024-01-17,A Distributed Magnetostatic Resonator,"This work reports the design, fabrication, and characterization of
coupling-enhanced magnetostatic forward volume wave resonators with significant
spur suppression. The fabrication is based on surface micro-machining of
yttrium iron garnet (YIG) film on a gadolinium gallium garnet (GGG) substrate
with thick gold transducers. A distributed resonator is used to excite forward
volume waves in YIG to realize a frequency dependent coupling boost. Fabricated
devices at 18 GHz and 7 GHz show coupling coefficients as high as 13$\%$ and
quality factors above 1000. Higher-order magnetostatic mode suppression is
experimentally demonstrated through a combination of transducer and YIG
geometry design. An edge-coupling filter topology is proposed and simulated
which utilizes this novel distributed magnetostatic resonator.",2401.08911v1
2013-08-17,Thickness and power dependence of the spin-pumping effect in Y3Fe5O12/Pt heterostructures measured by the inverse spin Hall effect,"The dependence of the spin-pumping effect on the yttrium iron garnet
(Y3Fe5O12, YIG) thickness detected by the inverse spin Hall effect (ISHE) has
been investigated quantitatively. Due to the spin-pumping effect driven by the
magnetization precession in the ferrimagnetic insulator YIG film a
spin-polarized electron current is injected into the Pt layer. This spin
current is transformed into electrical charge current by means of the ISHE. An
increase of the ISHE-voltage with increasing film thickness is observed and
compared to the theoretically expected behavior. The effective damping
parameter of the YIG/Pt samples is found to be enhanced with decreasing YIG
film thickness. The investigated samples exhibit a spin mixing conductance of
g=(7.43 \pm 0.36) \times 10^{18} m^{-2} and a spin Hall angle of theta_{ISHE} =
0.009 \pm 0.0008. Furthermore, the influence of nonlinear effects on the
generated voltage and on the Gilbert damping parameter at high excitation
powers are revealed. It is shown that for small YIG film thicknesses a
broadening of the linewidth due to nonlinear effects at high excitation powers
is suppressed because of a lack of nonlinear multi-magnon scattering channels.
We have found that the variation of the spin-pumping efficiency for thick YIG
samples exhibiting pronounced nonlinear effects is much smaller than the
nonlinear enhancement of the damping.",1308.3787v1
2014-02-15,Measurement of the intrinsic damping constant in individual nanodisks of YIG and YIG{\textbar}Pt,"We report on an experimental study on the spin-waves relaxation rate in two
series of nanodisks of diameter $\phi=$300, 500 and 700~nm, patterned out of
two systems: a 20~nm thick yttrium iron garnet (YIG) film grown by pulsed laser
deposition either bare or covered by 13~nm of Pt. Using a magnetic resonance
force microscope, we measure precisely the ferromagnetic resonance linewidth of
each individual YIG and YIG{\textbar}Pt nanodisks. We find that the linewidth
in the nanostructure is sensibly smaller than the one measured in the extended
film. Analysis of the frequency dependence of the spectral linewidth indicates
that the improvement is principally due to the suppression of the inhomogeneous
part of the broadening due to geometrical confinement, suggesting that only the
homogeneous broadening contributes to the linewidth of the nanostructure. For
the bare YIG nano-disks, the broadening is associated to a damping constant
$\alpha = 4 \cdot 10^{-4}$. A 3 fold increase of the linewidth is observed for
the series with Pt cap layer, attributed to the spin pumping effect. The
measured enhancement allows to extract the spin mixing conductance found to be
$G_{\uparrow \downarrow}= 1.55 \cdot 10^{14}~ \Omega^{-1}\text{m}^{-2}$ for our
YIG(20nm){\textbar}Pt interface, thus opening large opportunities for the
design of YIG based nanostructures with optimized magnetic losses.",1402.3630v1
2016-04-29,Spin Seebeck effect through antiferromagnetic NiO,"We report temperature-dependent spin-Seebeck measurements on Pt/YIG bilayers
and Pt/NiO/YIG trilayers, where YIG (Yttrium iron garnet, Y$_3$Fe$_5$O$_{12}$)
is an insulating ferrimagnet and NiO is an antiferromagnet at low temperatures.
The thickness of the NiO layer is varied from 0 to 10 nm. In the Pt/YIG
bilayers, the temperature gradient applied to the YIG stimulates dynamic spin
injection into the Pt, which generates an inverse spin Hall voltage in the Pt.
The presence of a NiO layer dampens the spin injection exponentially with a
decay length of $2 \pm 0.6$ nm at 180 K. The decay length increases with
temperature and shows a maximum of $5.5 \pm 0.8$ nm at 360 K. The temperature
dependence of the amplitude of the spin-Seebeck signal without NiO shows a
broad maximum of $6.5 \pm 0.5$ $\mu$V/K at 20 K. In the presence of NiO, the
maximum shifts sharply to higher temperatures, likely correlated to the
increase in decay length. This implies that NiO is most transparent to magnon
propagation near the paramagnet-antiferromagnet transition. We do not see the
enhancement in spin current driven into Pt reported in other papers when 1-2 nm
NiO layers are sandwiched between Pt and YIG.",1604.08659v2
2016-08-16,Probing current-induced magnetic fields in Au|YIG heterostructure with low-energy muon spectroscopy,"We investigated the depth dependence of current-induced magnetic fields in a
bilayer of a normal metal (Au) and a ferrimagnetic insulator (Yttrium Iron
Garnet - YIG) by using low energy muon spectroscopy (LE-muSR). This allows us
to explore how these fields vary from the Au surface down to the buried Au|YIG
interface, which is relevant to study physics like the spin-Hall effect. We
observed a maximum shift of 0.4 G in the internal field of muons at the surface
of Au film which is in close agreement to the value expected for Oersted
fields. As muons are implanted closer to the Au|YIG interface the shift is
strongly suppressed, which we attribute to the dipolar fields present at the
Au|YIG interface. Combining our measurements with modelling, we show that
dipolar fields caused by the finite roughness of the Au|YIG interface
consistently explains our observations. Our results, therefore, gauge the
limits on the spatial resolution and the sensitivity of LE-muSR to the
roughness of the buried magnetic interfaces, a prerequisite for future studies
addressing current induced fields caused by the spin-Hall effect.",1608.04584v1
2016-12-24,Impact of the interface quality of Pt/YIG(111) hybrids on their spin Hall magnetoresistance,"We study the influence of the interface quality of
Pt/Y$_3$Fe$_5$O$_{12}$(111) hybrids on their spin Hall magnetoresistance. This
is achieved by exposing Y$_3$Fe$_5$O$_{12}$(111) single crystal substrates to
different well-defined surface treatments prior to the Pt deposition. The
quality of the Y$_3$Fe$_5$O$_{12}$(YIG) surface, the Pt/YIG interface and the
Pt layer is monitored \textit{in-situ} by reflection high-energy electron
diffraction and Auger electron spectroscopy as well as \textit{ex-situ} by
atomic force microscopy and x-ray diffraction. To identify the impact of the
different surface treatments on the spin Hall magnetoresistance,
angle-dependent magnetoresistance measurements are carried out at room
temperature. The largest spin Hall magnetoresistance is found in Pt/YIG
fabricated by a two-step surface treatment consisting of a ""piranha"" etch
process followed by an annealing step at $500^\circ$C in pure oxygen
atmosphere. Our data suggest that the small SMR in Pt/YIG without any surface
treatments of the YIG substrate prior to Pt deposition is caused by a
considerable carbon agglomeration at the Y$_3$Fe$_5$O$_{12}$ surface.",1612.08150v1
2018-03-30,Nonlocal magnon spin transport in yttrium iron garnet with tantalum and platinum spin injection/detection electrodes,"We study the magnon spin transport in the magnetic insulator yttrium iron
garnet (YIG) in a nonlocal experiment and compare the magnon spin excitation
and detection for the heavy metal paramagnetic electrodes platinum (Pt|YIG|Pt)
and tantalum (Ta|YIG|Ta). The electrical injection and detection processes rely
on the (inverse) spin Hall effect in the heavy metals and the conversion
between the electron spin and magnon spin at the heavy metal|YIG interface. Pt
and Ta possess opposite signs of the spin Hall angle. Furthermore, their
heterostructures with YIG have different interface properties, i.e. spin mixing
conductances. By varying the distance between injector and detector, the magnon
spin transport is studied. Using a circuit model based on the
diffusion-relaxation transport theory, a similar magnon relaxation length of ~
10 \mu m was extracted from both Pt and Ta devices. By changing the injector
and detector material from Pt to Ta, the influence of interface properties on
the magnon spin transport has been observed. For Ta devices on YIG the spin
mixing conductance is reduced compared with Pt devices, which is quantitatively
consistent when comparing the dependence of the nonlocal signal on the
injector-detector distance with the prediction from the circuit model.",1803.11382v1
2018-08-17,Temperature Dependence of Magnetic Properties of an 18-nm-thick YIG Film Grown by Liquid Phase Epitaxy: Effect of a Pt Overlayer,"Liquid phase epitaxy of an 18 nm thick Yttrium Iron garnet (YIG) film is
achieved. Its magnetic properties are investigated in the 100 -- 400 K
temperature range, as well as the influence of a 3 nm thick Pt overlayer on
them. The saturation magnetization and the magnetocrystalline cubic anisotropy
of the bare YIG film behave similarly to bulk YIG. A damping parameter of only
a few $10^{-4}$ is measured, together with a low inhomogeneous contribution to
the ferromagnetic resonance linewidth. The magnetic relaxation increases upon
decreasing temperature, which can be partly ascribed to impurity relaxation
mechanisms. While it does not change its cubic anisotropy, the Pt capping
strongly affects the uniaxial perpendicular anisotropy of the YIG film, in
particular at low temperatures. The interfacial coupling in the YIG/Pt
heterostructure is also revealed by an increase of the linewidth, which
substantially grows by lowering the temperature.",1808.05785v2
2020-04-05,Spin wave based tunable switch between superconducting flux qubits,"Quantum computing hardware has received world-wide attention and made
considerable progress recently. YIG thin film have spin wave (magnon) modes
with low dissipation and reliable control for quantum information processing.
However, the coherent coupling between a quantum device and YIG thin film has
yet been demonstrated. Here, we propose a scheme to achieve strong coupling
between superconducting flux qubits and magnon modes in YIG thin film. Unlike
the direct $\sqrt{N}$ enhancement factor in coupling to the Kittel mode or
other spin ensembles, with N the total number of spins, an additional spatial
dependent phase factor needs to be considered when the qubits are magnetically
coupled with the magnon modes of finite wavelength. To avoid undesirable
cancelation of coupling caused by the symmetrical boundary condition, a CoFeB
thin layer is added to one side of the YIG thin film to break the symmetry. Our
numerical simulation demonstrates avoided crossing and coherent transfer of
quantum information between the flux qubits and the standing spin waves in YIG
thin films. We show that the YIG thin film can be used as a tunable switch
between two flux qubits, which have modified shape with small direct inductive
coupling between them. Our results manifest that it is possible to couple flux
qubits while suppressing undesirable cross-talk.",2004.02156v1
2021-04-16,Strong magnon-photon coupling with chip-integrated YIG in the zero-temperature limit,"The cross-integration of spin-wave and superconducting technologies is a
promising method for creating novel hybrid devices for future information
processing technologies to store, manipulate, or convert data in both classical
and quantum regimes. Hybrid magnon-polariton systems have been widely studied
using bulk Yttrium Iron Garnet (Y$_{3}$Fe$_{5}$O$_{12}$, YIG) and
three-dimensional microwave photon cavities. However, limitations in YIG growth
have thus far prevented its incorporation into CMOS compatible technology such
as high quality factor superconducting quantum technology. To overcome this
impediment, we have used Plasma Focused Ion Beam (PFIB) technology -- taking
advantage of precision placement down to the micron-scale -- to integrate YIG
with superconducting microwave devices. Ferromagnetic resonance has been
measured at millikelvin temperatures on PFIB-processed YIG samples using planar
microwave circuits. Furthermore, we demonstrate strong coupling between
superconducting resonator and YIG ferromagnetic resonance modes by maintaining
reasonably low loss while reducing the system down to the micron scale. This
achievement of strong coupling on-chip is a crucial step toward fabrication of
functional hybrid quantum devices that advantage from spin-wave and
superconducting components.",2104.08068v3
2019-02-01,Quantum thermodynamics of complex ferrimagnets,"High-quality magnets such as yttrium iron garnet (YIG) are electrically
insulating and very complex. By implementing a quantum thermostat into
atomistic spin dynamics we compute YIG's key thermodynamic properties, viz. the
magnon power spectrum and specific heat, for a large temperature range. The
results differ (sometimes spectacularly) from simple models and classical
statistics, but agree with available experimental data.",1902.00449v1
2012-11-01,Longitudinal Spin Seebeck Effect Free from the Proximity Nernst Effect,"This letter provides evidence for intrinsic longitudinal spin Seebeck effects
(LSSEs) that are free from the anomalous Nernst effect (ANE) caused by an
extrinsic proximity effect. We report the observation of LSSEs in Au/Y3Fe5O12
(YIG) and Pt/Cu/YIG systems, showing that LSSE appears even when the mechanism
of the proximity ANE is clearly removed. In the conventional Pt/YIG structure,
furthermore, we separate the LSSE from the ANE by comparing the voltages in
different magnetization and temperature-gradient configurations; the ANE
contamination was found to be negligibly small even in the Pt/YIG structure.",1211.0139v2
2013-01-15,Spin-Hall Magnetoresistance in Platinum on Yttrium Iron Garnet: Dependence on platinum thickness and in-plane/out-of-plane magnetization,"The occurrence of Spin-Hall Magnetoresistance (SMR) in platinum (Pt) on top
of yttrium iron garnet (YIG) has been investigated, for both in-plane and
out-of-plane applied magnetic fields and for different Pt thicknesses [3, 4, 8
and 35nm]. Our experiments show that the SMR signal directly depends on the
in-plane and out-of-plane magnetization directions of the YIG. This confirms
the theoretical description, where the SMR occurs due to the interplay of
spin-orbit interaction in the Pt and spin-mixing at the YIG/Pt interface.
Additionally, the sensitivity of the SMR and spin pumping signals on the YIG/Pt
interface conditions is shown by comparing two different deposition techniques
(e-beam evaporation and dc sputtering).",1301.3266v2
2013-09-19,Tuning Magnetotransport in PdPt/Y3Fe5O12: Effects of magnetic proximity and spin orbital coupling,"Anisotropic magnetoresistance (AMR) ratio and anomalous Hall conductivity
(AHC) in PdPt/Y$_3$Fe$_5$O$_{12}$ (YIG) system are tuned significantly by spin
orbital coupling strength $\xi$ through varying the Pt concentration. For both
Pt/YIG and Pd/YIG, the maximal AMR ratio is located at temperatures for the
maximal susceptibility of paramagnetic Pt and Pd metals. The AHC and ordinary
Hall effect both change the sign with temperature for Pt-rich system and vice
versa for Pd-rich system. The present results ambiguously evidence the spin
polarization of Pt and Pd atoms in contact with YIG layers. The global
curvature near the Fermi surface is suggested to change with the Pt
concentration and temperature.",1309.4841v2
2013-11-19,Observation of the spin Peltier effect,"We report the observation of the spin Peltier effect (SPE) in the
ferrimagnetic insulator Yttrium Iron Garnet (YIG), i.e. a heat current
generated by a spin current flowing through a Platinum (Pt)|YIG interface. The
effect can be explained by the spin torque that transforms the spin current in
the Pt into a magnon current in the YIG. Via magnon-phonon interactions the
magnetic fluctuations modulate the phonon temperature that is detected by a
thermopile close to the interface. By finite-element modelling we verify the
reciprocity between the spin Peltier and spin Seebeck effect. The observed
strong coupling between thermal magnons and phonons in YIG is attractive for
nanoscale cooling techniques.",1311.4772v1
2014-04-08,Modulation of pure spin currents with a ferromagnetic insulator,"We propose and demonstrate spin manipulation by magnetically controlled
modulation of pure spin currents in cobalt/copper lateral spin valves,
fabricated on top of the magnetic insulator Y$_3$Fe$_5$O$_{12}$ (YIG). The
direction of the YIG magnetization can be controlled by a small magnetic field.
We observe a clear modulation of the non-local resistance as a function of the
orientation of the YIG magnetization with respect to the polarization of the
spin current. Such a modulation can only be explained by assuming a finite
spin-mixing conductance at the Cu/YIG interface, as it follows from the
solution of the spin-diffusion equation. These results open a new path towards
the development of spin logics.",1404.2311v2
2015-03-25,Nature of magnetotransport in metal/insulating-ferromagnet heterostructures: Spin Hall magnetoresistance or magnetic proximity effect,"We study the anomalous Hall-like effect (AHLE) and the effective anisotropic
magnetoresistance (EAMR) in antiferromagnetic {\gamma} -IrMn3/Y3Fe5O12(YIG) and
Pt/YIG heterostructures. For {\gamma} -IrMn3/YIG, the EAMR and the AHLE
resistivity change sign with temperature due to the competition between the
spin Hall magnetoresistance (SMR) and the magnetic proximity effect (MPE)
induced by the interfacial antiferromagnetic uncompensated magnetic moment. In
contrast, for Pt/YIG the AHLE resistivity changes sign with temperature whereas
no sign change is observed in the EAMR. This is because the MPE and the SMR
play a dominant role in the AHLE and the EAMR, respectively. As new types of
galvanomagnetic property, the AHLE and the EAMR have proved vital in
disentangling the MPE and the SMR in metal/insulating-ferromagnet
heterostructures.",1503.07388v2
2015-05-29,Thermal conductance of thin film YIG determined using Bayesian statistics,"Thin film YIG (Y$_3$Fe$_5$O$_{12}$) is a prototypical material for
experiments on thermally generated pure spin currents and the spin Seebeck
effect. The 3-omega method is an established technique to measure the
cross-plane thermal conductance of thin films, but can not be used in YIG/GGG
(Ga$_3$Gd$_5$O$_{12}$) systems in its standard form. We use two-dimensional
modeling of heat transport and introduce a technique based on Bayesian
statistics to evaluate measurement data taken from the 3-omega method. Our
analysis method allows us to study materials systems that have not been
accessible with the conventionally used 3-omega analysis. Temperature dependent
thermal conductance data of thin film YIG are of major importance for
experiments in the field of spin-caloritronics. Here we show data between room
temperature and 10 K for films covering a wide thickness range as well as the
magnetic field effect on the thermal conductance between 10 K and 50 K.",1505.08006v1
2015-12-30,Non-equilibrium thermodynamics of the spin Seebeck and spin Peltier effects,"We study the problem of magnetization and heat currents and their associated
thermodynamic forces in a magnetic system by focusing on the magnetization
transport in ferromagnetic insulators like YIG. The resulting theory is applied
to the longitudinal spin Seebeck and the spin Peltier effects. By focusing on
the specific geometry with one YIG layer and one Pt layer, we obtain the
optimal conditions for generating large magnetization currents into Pt or large
temperature effects in YIG. The theoretical predictions are compared with
experiments from the literature permitting to derive the values of the
thermomagnetic coefficients of YIG: the magnetization diffusion length $l_M
\sim 0.4 \, \mu$m and the absolute thermomagnetic power coefficient $\epsilon_M
\sim 10^{-2}$ TK$^{-1}$.",1512.08890v2
2016-03-02,Enhancement of Thermally Injected Spin Current through an Antiferromagnetic Insulator,"We report large enhancement of thermally injected spin current in normal
metal (NM)/antiferromagnet(AF)/yttrium iron garnet(YIG), where a thin AF
insulating layer of NiO or CoO can enhance spin current from YIG to a NM by up
to a factor of 10. The spin current enhancement in NM/AF/YIG, with a pronounced
maximum near the N\'eel temperature of the thin AF layer, has been found to
scale linearly with the spin-mixing conductance at the NM/YIG interface for NM
= 3d, 4d, and 5d metals. Calculations of spin current enhancement and spin
mixing conductance are qualitatively consistent with the experimental results.",1603.00931v2
2016-06-09,"Competing effects at Pt/YIG interfaces: spin Hall magnetoresistance, magnon excitations and magnetic frustration","We study the spin Hall magnetoresistance (SMR) and the magnon spin transport
(MST) in Pt/Y3Fe5O12(YIG)-based devices with intentionally modified interfaces.
Our measurements show that the surface treatment of the YIG film results in a
slight enhancement of the spin-mixing conductance and an extraordinary increase
in the efficiency of the spin-to-magnon excitations at room temperature. The
surface of the YIG film develops a surface magnetic frustration at low
temperatures, causing a sign change of the SMR and a dramatic suppression of
the MST. Our results evidence that SMR and MST could be used to explore
magnetic properties of surfaces, including those with complex magnetic
textures, and stress the critical importance of the non-magnetic/ferromagnetic
interface properties in the performance of the resulting spintronic devices.",1606.02968v2
2017-01-10,Temperature dependence of the non-local spin Seebeck effect in YIG/Pt nanostructures,"We study the transport of thermally excited non-equilibrium magnons through
the ferrimagnetic insulator YIG using two electrically isolated Pt strips as
injector and detector. The diffusing magnons induce a non- local inverse spin
Hall voltage in the detector corresponding to the so-called non-local spin
Seebeck effect (SSE). We measure the non-local SSE as a function of temperature
and strip separation. In experiments at room temperature we observe a sign
change of the non-local SSE voltage at a characteristic strip separation d0, in
agreement with previous investigations. At lower temperatures however, we find
a strong temperature dependence of d0. This suggests that both the angular
momentum transfer across the YIG/Pt interface as well as the transport
mechanism of the magnons in YIG as a function of temperature must be taken into
account to describe the non-local spin Seebeck effect.",1701.02635v1
2017-04-25,Probing length-scale separation of thermal and spin currents by nanostructuring YIG,"We have fabricated bulk nanostructured ferrimagnetic materials with different
grain sizes by sintering ball-milled Y3Fe5O12 (YIG) nanoparticles and measured
the grain-size dependence of the thermal conductivity and spin Seebeck
thermopower. The nanostructuring reduces both thermal conductivity and
thermopower, but the reduction of the latter was found to be considerably
stronger despite the moderate difference in magnetization, which suggests that
the length scales of transport of magnons and phonons contributing to the spin
Seebeck effect are significantly larger than that of phonons carrying thermal
current. This is consistent with the measurements of high-magnetic-field
response of the spin Seebeck thermopower and low-temperature thermal
conductivity, where the quenching of magnons seen in single-crystalline YIG was
not observed in nanostructured YIG due to scattering of long-range low
frequency magnons.",1704.07568v1
2017-09-12,Direct observation of magnon-phonon coupling in yttrium iron garnet,"The magnetic insulator yttrium iron garnet (YIG) with a ferrimagnetic
transition temperature of $\sim$560 K has been widely used in microwave and
spintronic devices. Anomalous features in the spin Seeback effect (SSE)
voltages have been observed in Pt/YIG and attributed to the magnon-phonon
coupling. Here we use inelastic neutron scattering to map out low-energy spin
waves and acoustic phonons of YIG at 100 K as a function of increasing magnetic
field. By comparing the zero and 9.1 T data, we find that instead of splitting
and opening up gaps at the spin wave and acoustic phonon dispersion
intersecting points, magnon-phonon coupling in YIG enhances the hybridized
scattering intensity. These results are different from expectations of
conventional spin-lattice coupling, calling for new paradigms to understand the
scattering process of magnon-phonon interactions and the resulting
magnon-polarons.",1709.03940v1
2017-11-27,"Magnetic properties, spin waves and interaction between spin excitations and 2D electrons in interface layer in Y3Fe5O12 / AlOx / GaAs-heterostructures","We describe synthesis of submicron Y3Fe5O12 (YIG) films sputtered on
GaAs-based substrates and present results of the investigation of ferromagnetic
resonance (FMR), spin wave propagation and interaction between spin excitations
and 2D electrons in interface layer in YIG / AlOx / GaAs-heterostructures. It
is found that the contribution of the relaxation process to the FMR linewidth
is about 2 % of the linewidth \Delta H. At the same time, for all samples FMR
linewidths are high. Sputtered YIG films have magnetic inhomogeneity, which
gives the main contribution to the FMR linewidth. Transistor structures with
two-dimensional electron gas (2DEG) channels in AlOx / GaAs interface governed
by YIG-film spin excitations are designed. An effective influence of spin
excitations on the current flowing through the GaAs 2DEG channel is observed.
Light illumination results in essential changes in the FMR spectrum. It is
found that an increase of the 2DEG current leads to an inverse effect, which
represents essential changes in the FMR spectrum.",1711.09814v1
2018-04-30,Single-Nitrogen-vacancy-center quantum memory for a superconducting flux qubit mediated by a ferromagnet,"We propose a quantum memory scheme to transfer and store the quantum state of
a superconducting flux qubit (FQ) into the electron spin of a single
nitrogen-vacancy (NV) center in diamond via yttrium iron garnet (YIG), a
ferromagnet. Unlike an ensemble of NV centers, the YIG moderator can enhance
the effective FQ-NV-center coupling strength without introducing additional
appreciable decoherence. We derive the effective interaction between the FQ and
the NV center by tracing out the degrees of freedom of the collective mode of
the YIG spins. We demonstrate the transfer, storage, and retrieval procedures,
taking into account the effects of spontaneous decay and pure dephasing. Using
realistic experimental parameters for the FQ, NV center and YIG, we find that a
combined transfer, storage, and retrieval fidelity higher than 0.9, with a long
storage time of 10 ms, can be achieved. This hybrid system not only acts as a
promising quantum memory, but also provides an example of enhanced coupling
between various systems through collective degrees of freedom.",1804.11231v1
2019-02-12,Characterization of spin wave propagation in (111) YIG thin films with large anisotropy,"We report on long-range spin wave (SW) propagation in nanometer-thick yttrium
iron garnet (YIG) film with an ultralow Gilbert damping. The knowledge of a
wavenumber value $|\vec{k}|$ is essential for designing SW devices. Although
determining the wavenumber $|\vec{k}|$ in experiments like Brillouin light
scattering spectroscopy is straightforward, quantifying the wavenumber in
all-electrical experiments has not been widely commented upon so far. We
analyze magnetostatic spin wave (SW) propagation in YIG films in order to
determine the SW wavenumber $|\vec{k}|$ excited by the coplanar waveguide. We
show that it is crucial to consider the influence of magnetic anisotropy fields
present in YIG thin films for precise determination of SW wavenumber. With the
proposed methods we find that experimentally derived values of $|\vec{k}|$ are
in perfect agreement with that obtained from electromagnetic simulation only if
anisotropy fields are included.",1902.04608v1
2019-04-09,Ferromagnetic Resonance Studies of Strain tuned Bi:YIG Films,"Bismuth-doped Yttrium iron garnet (Bi:YIG) thin films known for large
Magneto-optical activity with low losses still needs to get probed for its
magnetization dynamics. We demonstrate a controlled tuning of
magnetocrystalline anisotropy in Bi-doped Y_3 Fe_5 O_12 (Bi:YIG) films of high
crystalline quality using growth induced epitaxial strain on [111]-oriented
Gd_3 Ga_5 O_12 (GGG) substrate. We optimize a growth protocol to get thick
highly-strained epitaxial films showing large magneto-crystalline anisotropy,
compare to thin films prepared using a different protocol. Ferromagnetic
resonance measurements establish a linear dependence of the out-of-plane
uniaxial anisotropy on the strain induced rhombohedral distortion of Bi:YIG
lattice. Interestingly, the enhancement in the magnetoelastic constant due to
an optimum substitution of Bi^(3+) ions with strong spin orbit coupling does
not strongly affect the precessional damping (~2x10^(-3) ). Large
magneto-optical activity, reasonably low damping, large magnetocrystalline
anisotropy and large magnetoelastic coupling in BiYIG are the properties that
may help BiYIG emerge as a possible material for photo-magnonics and other
spintronics applications.",1904.04800v2
2019-04-23,Current-induced switching of YIG/Pt bilayers with in-plane magnetization due to Oersted fields,"We report on the switching of the in-plane magnetization of thin yttrium iron
garnet (YIG)/Pt bilayers induced by an electrical current. The switching is
either field-induced and assisted by a dc current, or current-induced and
assisted by a static magnetic field. The reversal of the magnetization occurs
at a current density as low as $10^5$~A/cm$^{2}$ and magnetic fields of $\sim
40$~$\mu$T, two orders of magnitude smaller than in ferromagnetic metals,
consistently with the weak uniaxial anisotropy of the YIG layers. We use the
transverse component of the spin Hall magnetoresistance to sense the magnetic
orientation of YIG while sweeping the current. Our measurements and simulations
reveal that the current-induced effective field responsible for switching is
due to the Oersted field generated by the current flowing in the Pt layer
rather than by spin-orbit torques, and that the switching efficiency is
influenced by pinning of the magnetic domains.",1904.10517v1
2019-09-09,Modulation of magnon spin transport in a magnetic gate transistor,"We demonstrate a modulation of up to 18% in the magnon spin transport in a
magnetic insulator (Y$_{3}$Fe$_{5}$O$_{12}$, YIG) using a common ferromagnetic
metal (permalloy, Py) as a magnetic control gate. A Py electrode, placed
between two Pt injector and detector electrodes, acts as a magnetic gate in our
prototypical magnon transistor device. By manipulating the magnetization
direction of Py with respect to that of YIG, the transmission of magnons
through the Py|YIG interface can be controlled, resulting in a modulation of
the non-equilibrium magnon density in the YIG channel between the Pt injector
and detector electrodes. This study opens up the possibility of using the
magnetic gating effect for magnon-based spin logic applications.",1909.03775v1
2020-01-15,Yttrium Iron Garnet Thickness Influence on the Spin Pumping in the Bulk Acoustic Wave Resonator,"The features of phonon-magnon interconversion in acoustic resonator determine
the efficiency of spin pumping from YIG into Pt that may be detected
electrically through the inverse spin Hall effect (ISHE). Based on the methods
developed in previous works for calculating resonator structures with a
piezoelectric (ZnO) and a magnetoelastic layer in contact with the heavy metal
(YIG/Pt), we present the results of numerical calculations of YIG film
thickness influence on acoustically driven spin waves. We obtain some YIG film
thickness regions with various behavior of dc ISHE voltage $U_{ISHE}$. At
micron and submicron thicknesses, the higher spin wave resonance (SWR) modes
(both even and odd) can be generated with efficiency comparable and even
exceeding that of the main mode. The absolute maximum of $U_{ISHE}$ is achieved
at the thickness about $s_1 \approx 208$ nm under the excitation of the first
SWR.",2001.05385v1
2020-02-28,Spin Hall magnetoresistance in Pt/YIG bilayers via varying magnon excitation,"Spin Hall magnetoresistance (SMR) and magnon excitation magnetoresistance
(MMR) that all generate via the spin Hall effect and inverse spin Hall effect
in a nonmagnetic material are always related to each other. However, the
influence of magnon excitation for SMR is often overlooked due to the
negligible MMR. Here, we investigate the SMR in Pt/Y3Fe5O12 (YIG) bilayers from
5 to 300K, in which the YIG are treated after Ar+-ion milling. The SMR in the
treated device is smaller than in the non-treated. According to theoretical
simulation, we attribute this phenomenon to the reduction of the interfacial
spin-mixing conductance at the treated Pt/YIG interface induced by the magnon
suppression. Our experimental results point out that the SMR and the MMR are
inter-connected, and the former could be modulated via magnon excitation. Our
findings provide a new approach for separating and clarifying the underlying
mechanisms.",2002.12550v1
2021-01-08,Compact tunable YIG-based RF resonators,"We report on the design, fabrication, and characterization of compact tunable
yttrium iron garnet (YIG) based RF resonators based on $\mu$m-sized spin-wave
cavities. Inductive antennas with both ladder and meander configurations were
used as transducers between spin waves and RF signals. The excitation of
ferromagnetic resonance and standing spin waves in the YIG cavities led to
sharp resonances with quality factors up to 350. The observed spectra were in
excellent agreement with a model based on the spin-wave dispersion relations in
YIG, showing a high magnetic field tunability of about 29 MHz/mT.",2101.02909v4
2022-11-27,Entangled atomic ensemble and an yttrium-iron-garnet sphere in coupled microwave cavities,"We present a scheme to generate distant bipartite and tripartite entanglement
between an atomic ensemble and an yttrium iron garnet (YIG) sphere in coupled
microwave cavities. We consider an atomic ensemble in a single-mode microwave
cavity which is coupled with a second single-mode cavity having a YIG sphere.
Our system, therefore, has five excitation modes namely cavity-1 photons,
atomic ensemble, cavity-2 photons, a magnon and a phonon mode in the YIG
sphere. We show that significant bipartite entanglement exists between
indirectly coupled subsystems in the cavities, which is robust against
temperature. Moreover, we present suitable parameters for a significant
tripartite entanglement of ensemble, magnon, and phonon modes. We also
demonstrate the existence of tripartite entanglement between magnon and phonon
modes of the YIG sphere with indirectly coupled cavity photons. Interestingly,
this distant tripartite entanglement is of the same order as previously found
for a single-cavity system. We show that cavity-cavity coupling strength
affects both the degree and transfer of quantum entanglement between various
subsystems. Therefore, an appropriate cavity-cavity coupling optimizes the
distant entanglement by increasing the entanglement strength and its robustness
against temperature.",2211.14914v2
2023-06-05,Spin Hall magnetoresistance in Pt/Y$_{3}$Fe$_{5}$O$_{12}$ bilayers grown on Si and Gd$_{3}$Ga$_{5}$O$_{12}$ substrates,"We study spin Hall magnetoresistance (SMR) in Pt/ferrimagnetic insulator
Y$_{3}$Fe$_{5}$O$_{12}$ (YIG) bilayers by focusing on crystallinity,
magnetization, and interface roughness by controlling post-annealing
temperatures. The SMR in the Pt/YIG grown on Si substrate is comparable to that
grown on widely used Gd$_{3}$Ga$_{5}$O$_{12}$ substrate, indicating that the
large SMR can be achieved irrespective to the crystallinity. We deduced the
spin mixing conductance from the Pt thickness dependence of the SMR to find the
high interface quality of the optimized Pt/YIG grown on Si in terms of spin
current. We also clarified that the SMR correlates well with the magnetization,
the interface roughness, and carrier density. These findings highlight that
optimizing YIG properties is a key to control of magnetization by spin current,
leading to the development of low power consumption spintronic device based on
the magnetic insulator.",2306.02575v1
2024-01-17,Giant Enhancement of Vacuum Friction in Spinning YIG Nanospheres,"Experimental observations of vacuum radiation and vacuum frictional torque
are challenging due to their vanishingly small effects in practical systems.
For example, a rotating nanosphere in free space slows down due to friction
from vacuum fluctuations with a stopping time around the age of the universe.
Here, we show that a spinning yttrium iron garnet (YIG) nanosphere near
aluminum or YIG slabs exhibits vacuum radiation eight orders of magnitude
larger than other metallic or dielectric spinning nanospheres. We achieve this
giant enhancement by exploiting the large near-field magnetic local density of
states in YIG systems, which occurs in the low-frequency GHz regime comparable
to the rotation frequency. Furthermore, we propose a realistic experimental
setup for observing the effects of this large vacuum radiation and frictional
torque under experimentally accessible conditions.",2401.09563v1
2024-03-05,Generation of gigahertz frequency surface acoustic waves in YIG/ZnO heterostructures,"We study surface acoustic waves (SAWs) in yttrium iron garnet (YIG)/zinc
oxide (ZnO) heterostructures, comparing the results of a computationally
lightweight analytical model with time-resolved micro-focused Brillouin light
scattering data. Interdigital transducers (IDTs), with operational frequencies
in the gigahertz regime, were fabricated on 50 and 100nm thin films of YIG
prior to sputter deposition of 830nm and 890nm films of piezoelectric ZnO. We
find good agreement between our analytical model and micro-focused Brillouin
light scattering data of the IDT frequency response and SAW group velocity,
with clear differentiation between the Rayleigh and Sezawa-like modes. This
work paves the way for the study of SAW-spin wave (SW) interactions in low SW
damping YIG, with the possibility of a method for future energy-efficient SW
excitation.",2403.03006v1
2024-02-19,Magnetic anisotropy and GGG substrate stray field in YIG films down to millikelvin temperatures,"Quantum magnonics investigates the quantum-mechanical properties of magnons
such as quantum coherence or entanglement for solid-state quantum information
technologies at the nanoscale. The most promising material for quantum
magnonics is the ferrimagnetic yttrium iron garnet (YIG), which hosts magnons
with the longest lifetimes. YIG films of the highest quality are grown on a
paramagnetic gadolinium gallium garnet (GGG) substrate. The literature has
reported that ferromagnetic resonance (FMR) frequencies of YIG/GGG decrease at
temperatures below 50 K despite the increase in YIG magnetization. We
investigated a 97 nm-thick YIG film grown on 500 $\mathrm{\mu}$m-thick GGG
substrate through a series of experiments conducted at temperatures as low as
30 mK, and using both analytical and numerical methods. Our findings suggest
that the primary factor contributing to the FMR frequency shift is the stray
magnetic field created by the partially magnetized GGG substrate. This stray
field is antiparallel to the applied external field and is highly
inhomogeneous, reaching up to 40 mT in the center of the sample. At
temperatures below 500 mK, the GGG field exhibits a saturation that cannot be
described by the standard Brillouin function for a paramagnet. Including the
calculated GGG field in the analysis of the FMR frequency versus temperature
dependence allowed the determination of the cubic and uniaxial anisotropies. We
find that the total anisotropy increases more than three times with the
decrease in temperature down to 2 K. Our findings enable accurate predictions
of the YIG/GGG magnetic systems behavior at low and ultra-low millikelvin
temperatures, crucial for developing quantum magnonic devices.",2402.12112v1
2015-12-02,Thermodynamics of the heat currents in the longitudinal spin Seebeck and spin Peltier effects,"We employ the non-equilibrium thermodynamics of currents and forces to
describe the heat transport caused by a spin current in a Pt/YIG bilayer. By
starting from the constitutive equations of the magnetization currents in both
Pt and YIG, we derive the magnetization potentials and currents. We apply the
theory to the spin Peltier experiments in which a spin current, generated by
the spin Hall effect in Pt, is injected into YIG. We find that efficient
injection is obtained when: i) the thickness of each layer is larger than its
diffusion length: $t_{Pt} > l_{Pt}$ and $t_{YIG} > l_{YIG}$ and ii) the ratio
$(l_{Pt}/\tau_{Pt})/(l_{YIG}/\tau_{YIG})$ is small, where $\tau_i$ is the time
constant of the intrinsic damping ($i=Pt, YIG$). We finally derive the
temperature profile in adiabatic conditions. The scale of the effect is given
by the parameter $\Delta T_{SH}$ which is proportional to the electric current
in Pt. Using known parameters for Pt and YIG we estimate $\Delta T_{SH}/j_e = 4
\cdot 10^{-13}$ K A$^{-1}$m$^2$. This value is of the same order of magnitude
of the spin Peltier experiments.",1512.00644v2
2016-12-22,Imaging Magnetization Structure and Dynamics in Ultrathin YIG/Pt Bilayers with High Sensitivity Using the Time-Resolved Longitudinal Spin Seebeck Effect,"We demonstrate an instrument for time-resolved magnetic imaging that is
highly sensitive to the in-plane magnetization state and dynamics of thin-film
bilayers of yttrium iron garnet (Y3Fe5O12,YIG)/Pt: the time-resolved
longitudinal spin Seebeck (TRLSSE) effect microscope. We detect the local,
in-plane magnetic orientation within the YIG by focusing a picosecond laser to
generate thermally-driven spin current from the YIG into the Pt by the spin
Seebeck effect, and then use the inverse spin Hall effect in the Pt to
transduce this spin current to an output voltage. To establish the time
resolution of TRLSSE, we show that pulsed optical heating of patterned YIG (20
nm)/Pt(6 nm)/Ru (2 nm) wires generates a magnetization-dependent voltage pulse
of less than 100 ps. We demonstrate TRLSSE microscopy to image both static
magnetic structure and gigahertz-frequency magnetic resonance dynamics with
sub-micron spatial resolution and a sensitivity to magnetic orientation below
0.3$^{\circ}/\sqrt{\text{Hz}}$ in ultrathin YIG.",1612.07610v2
2017-03-26,Unexpected structural and magnetic depth dependence of YIG thin films,"We report measurements on yttrium iron garnet (YIG) thin films grown on both
gadolinium gallium garnet (GGG) and yttrium aluminium garnet (YAG) substrates,
with and without thin Pt top layers. We provide three principal results: the
observation of an interfacial region at the Pt/YIG interface, we place a limit
on the induced magnetism of the Pt layer and confirm the existence of an
interfacial layer at the GGG/YIG interface. Polarised neutron reflectometry
(PNR) was used to give depth dependence of both the structure and magnetism of
these structures. We find that a thin film of YIG on GGG is best described by
three distinct layers: an interfacial layer near the GGG, around 5 nm thick and
non-magnetic, a magnetic bulk phase, and a non-magnetic and compositionally
distinct thin layer near the surface. We theorise that the bottom layer, which
is independent of the film thickness, is caused by Gd diffusion. The top layer
is likely to be extremely important in inverse spin Hall effect measurements,
and is most likely Y2O3 or very similar. Magnetic sensitivity in the PNR to any
induced moment in the Pt is increased by the existence of the Y2O3 layer; any
moment is found to be less than 0.02 uB/atom.",1703.08752v1
2017-11-20,Temperature dependent relaxation of dipole-exchange magnons in yttrium iron garnet films,"Low energy consumption enabled by charge-free information transport, which is
free from ohmic heating, and the ability to process phase-encoded data by
nanometer-sized interference devices at GHz and THz frequencies are just a few
benefits of spin-wave-based technologies. Moreover, when approaching cryogenic
temperatures, quantum phenomena in spin-wave systems pave the path towards
quantum information processing. In view of these applications, the lifetime of
magnons$-$spin-wave quanta$-$is of high relevance for the fields of magnonics,
magnon spintronics and quantum computing. Here, the relaxation behavior of
parametrically excited magnons having wavenumbers from zero up to $6\cdot 10^5
\mathrm{rad~cm}^{-1}$ was experimentally investigated in the temperature range
from 20 K to 340 K in single crystal yttrium iron garnet (YIG) films
epitaxially grown on gallium gadolinium garnet (GGG) substrates as well as in a
bulk YIG crystal$-$the magnonic materials featuring the lowest magnetic damping
known so far. As opposed to the bulk YIG crystal in YIG films we have found a
significant increase in the magnon relaxation rate below 150 K$-$up to 10.5
times the reference value at 340 K$-$in the entire range of probed wavenumbers.
This increase is associated with rare-earth impurities contaminating the YIG
samples with a slight contribution caused by coupling of spin waves to the spin
system of the paramagnetic GGG substrate at the lowest temperatures.",1711.07517v1
2018-02-26,Spin Seebeck effect and ballistic transport of quasi-acoustic magnons in room-temperature yttrium iron garnet films,"We studied the transient behavior of the spin current generated by the
longitudinal spin Seebeck effect (LSSE) in a set of platinum-coated yttrium
iron garnet (YIG) films of different thicknesses. The LSSE was induced by means
of pulsed microwave heating of the Pt layer and the spin currents were measured
electrically using the inverse spin Hall effect in the same layer. We
demonstrate that the time evolution of the LSSE is determined by the evolution
of the thermal gradient triggering the flux of thermal magnons in the vicinity
of the YIG/Pt interface. These magnons move ballistically within the YIG film
with a constant group velocity, while their number decays exponentially within
an effective propagation length. The ballistic flight of the magnons with
energies above 20K is a result of their almost linear dispersion law, similar
to that of acoustic phonons. By fitting the time-dependent LSSE signal for
different film thicknesses varying by almost an order of magnitude, we found
that the effective propagation length is practically independent of the YIG
film thickness. We consider this fact as strong support of a ballistic
transport scenario - the ballistic propagation of quasi-acoustic magnons in
room temperature YIG.",1802.09593v1
2019-06-28,Spin transport in an insulating ferrimagnetic-antiferromagnetic-ferrimagnetic trilayer as a function of temperature,"We present a study of the transport properties of thermally generated spin
currents in an insulating ferrimagnetic-antiferromagnetic-ferrimagnetic
trilayer over a wide range of temperature. Spin currents generated by the spin
Seebeck effect (SSE) in a yttrium iron garnet (YIG) YIG/NiO/YIG trilayer on a
gadolinium gallium garnet (GGG) substrate were detected using the inverse spin
Hall effect in Pt. By studying samples with different NiO thicknesses, the NiO
spin diffusion length was determined to be 4.2 nm at room temperature.
Interestingly, below 30 K, the inverse spin Hall signals are associated with
the GGG substrate. The field dependence of the signal follows a Brillouin
function for a S=7/2 spin ($\mathrm{Gd^{3+}}$) at low temperature. Sharp
changes in the SSE signal at low fields are due to switching of the YIG
magnetization. A broad peak in the SSE response was observed around 100 K,
which we associate with an increase in the spin-diffusion length in YIG. These
observations are important in understanding the generation and transport
properties of spin currents through magnetic insulators and the role of a
paramagnetic substrate in spin current generation.",1906.12288v1
2019-11-21,Low damping and microstructural perfection of sub-40nm-thin yttrium iron garnet films grown by liquid phase epitaxy,"The field of magnon spintronics is experiencing an increasing interest in the
development of solutions for spin-wave-based data transport and processing
technologies that are complementary or alternative to modern CMOS
architectures. Nanometer-thin yttrium iron garnet (YIG) films have been the
gold standard for insulator-based spintronics to date, but a potential process
technology that can deliver perfect, homogeneous large-diameter films is still
lacking. We report that liquid phase epitaxy (LPE) enables the deposition of
nanometer-thin YIG films with low ferromagnetic resonance losses and
consistently high magnetic quality down to a thickness of 20 nm. The obtained
epitaxial films are characterized by an ideal stoichiometry and perfect film
lattices, which show neither significant compositional strain nor geometric
mosaicity, but sharp interfaces. Their magneto-static and dynamic behavior is
similar to that of single crystalline bulk YIG. We found, that the Gilbert
damping coefficient alpha is independent of the film thickness and close to 1 x
10-4, and that together with an inhomogeneous peak-to-peak linewidth broadening
of delta H0|| = 0.4 G, these values are among the lowest ever reported for YIG
films with a thickness smaller than 40 nm. These results suggest, that
nanometer-thin LPE films can be used to fabricate nano- and micro-scaled
circuits with the required quality for magnonic devices. The LPE technique is
easily scalable to YIG sample diameters of several inches.",1911.09400v1
2021-09-10,Electrical spectroscopy of the spin-wave dispersion and bistability in gallium-doped yttrium iron garnet,"Yttrium iron garnet (YIG) is a magnetic insulator with record-low damping,
allowing spin-wave transport over macroscopic distances. Doping YIG with
gallium ions greatly reduces the demagnetizing field and introduces a
perpendicular magnetic anisotropy, which leads to an isotropic spin-wave
dispersion that facilitates spin-wave optics and spin-wave steering. Here, we
characterize the dispersion of a gallium-doped YIG (Ga:YIG) thin film using
electrical spectroscopy. We determine the magnetic anisotropy parameters from
the ferromagnetic resonance frequency and use propagating spin wave
spectroscopy in the Damon-Eshbach configuration to detect the small spin-wave
magnetic fields of this ultrathin weak magnet over a wide range of wavevectors,
enabling the extraction of the exchange constant $\alpha=1.3(2)\times10^{-12}$
J/m. The frequencies of the spin waves shift with increasing drive power, which
eventually leads to the foldover of the spin-wave modes. Our results shed light
on isotropic spin-wave transport in Ga:YIG and highlight the potential of
electrical spectroscopy to map out the dispersion and bistability of
propagating spin waves in magnets with a low saturation magnetization.",2109.05045v1
2022-03-30,Tunable magnetically induced transparency spectra in magnon-magnon coupled Y3Fe5O12/permalloy bilayers,"Hybrid magnonic systems host a variety of characteristic quantum phenomena
such as the magnetically-induced transparency (MIT) and Purcell effect, which
are considered useful for future coherent quantum information processing. In
this work, we experimentally demonstrate a tunable MIT effect in the
Y3Fe5O12(YIG)/Permalloy(Py) magnon-magnon coupled system via changing the
magnetic field orientations. By probing the magneto-optic effects of Py and
YIG, we identify clear features of MIT spectra induced by the mode
hybridization between the uniform mode of Py and the perpendicular standing
spin-wave modes of YIG. By changing the external magnetic field orientations,
we observe a tunable coupling strength between the YIG's spin-wave modes and
the Py's uniform mode, upon the application of an out-of-plane magnetic field.
This observation is theoretically interpreted by a geometrical consideration of
the Py and YIG magnetization under the oblique magnetic field even at a
constant interfacial exchange coupling. Our findings show high promise for
investigating tunable coherent phenomena with hybrid magnonic platforms.",2203.16303v1
2023-01-16,Crystal orientation dependent spin pumping in Bi0.1Y2.9Fe5O12/Pt interface,"Ferromagnetic resonance (FMR) based spin pumping is a versatile tool to
quantify the spin mixing conductance and spin to charge conversion (S2CC)
efficiency of ferromagnet/normal metal (FM/NM) heterostructure. The spin mixing
conductance of FM/NM interface can also be tuned by the crystal orientation
symmetry of epitaxial FM. In this work, we study the S2CC in epitaxial Bismuth
substituted Yttrium Iron Garnet (Bi0.1Y2.9Fe5O12) thin films Bi-YIG (100 nm)
interfaced with heavy metal platinum (Pt (8 nm)) deposited by pulsed laser
deposition process on different crystal orientation Gd3Ga5O12 (GGG) substrates
i.e. [100] and [111]. The crystal structure and surface roughness characterized
by X-Ray diffraction and atomic force microscopy measurements establish
epitaxial Bi-YIG[100], Bi-YIG[111] orientations and atomically flat surfaces
respectively. The S2CC quantification has been realized by two complimentary
techniques, (i) FMR-based spin pumping and inverse spin Hall effect (ISHE) at
GHz frequency and (ii) temperature dependent spin Seebeck measurements.
FMR-ISHE results demonstrate that the [111] oriented Bi-YIG/Pt sample shows
significantly higher values of spin mixing conductance ((2.31+-0.23)x10^18
m^-2) and spin Hall angle (0.01+-0.001) as compared to the [100] oriented
Bi-YIG/Pt. A longitudinal spin Seebeck measurement reveals that the [111]
oriented sample has higher spin Seebeck coefficient (106.40+-10 nV mm-1 K-1).
This anisotropic nature of spin mixing conductance and spin Seebeck coefficient
in [111] and [100] orientation has been discussed using the magnetic
environment elongation along the surface normal or parallel to the growth
direction. Our results aid in understanding the role of crystal orientation
symmetry in S2CC based spintronics devices.",2301.06477v1
2020-02-02,A millimeter-wave Bell Test using a ferrite parametric amplifier and a homodyne interferometer,"A combined ferrite parametric amplifier and millimeter-wave homodyne
interferometer are proposed as an ambient temperature Bell Test. It is shown
that the non-linear magnetic susceptibility of the yttrium iron garnet (YIG)
ferrite, on account of its narrow line-width Larmor precessional resonance,
make it an ideal material for the creation of entangled photons. These can be
measured using a homodyne interferometer, as the much larger number of
thermally generated photons associated with ambient temperature emission can be
screened out. The proposed architecture may enable YIG quantum technology-based
sensors to be developed, mimicking in the millimeter-wave band the large number
of quantum optical experiments in the near-infrared and visible regions which
had been made possible by use of the nonlinear beta barium borate
ferroelectric, an analogue of YIG. It is illustrated here how the YIG
parametric amplifier can reproduce quantum optical Type I and Type II wave
interactions, which can be used to create entangled photons in the
millimeter-wave band. It is estimated that when half a cubic centimeter of YIG
crystal is placed in a magnetic field of a few Tesla and pumped with 5 Watts of
millimeter-wave radiation, approximately 0.5x10^12 entangled millimeter-wave
photon pairs per second are generated by the spin-wave interaction. This means
an integration time of only a few tens of seconds is needed for a successful
Bell Test. A successful demonstration of this will lead to novel architectures
of entanglement-based quantum technology room temperature sensors,
re-envisioning YIG as a modern quantum material.",2002.00439v3
2024-02-01,Exploring inverse orbital Hall and orbital Rashba effects: unveiling the oxidation states of the Cu surface,"In this work, employing spin-pumping techniques driven by both ferromagnetic
resonance (SP-FMR) and longitudinal spin Seebeck effect (LSSE) to manipulate
and direct observe orbital currents, we investigated the volume conversion of
spin-orbital currents into charge-current in YIG(100nm)/Pt(2nm)/NM2 structures,
where NM2 represents Ti or Ru. While the YIG/Ti bilayer displayed a negligible
SP-FMR signal, the YIG/Pt/Ti structure exhibited a significantly stronger
signal attributed to the orbital Hall effect of Ti. Substituting the Ti layer
with Ru revealed a similar phenomenon, wherein the effect is ascribed to the
combined action of both spin and orbital Hall effects. Furthermore, we measured
the SP-FMR signal in the YIG/Pt(2)/Ru(6)/Ti(6) and YIG/Pt(2)/Ti(6)/Ru(6)
heterostructures by just altering the stack order of Ti and Ru layers, where
the peak value of the spin pumping signal is larger for the first sample. To
verify the influence on the oxidation of Ti and Ru films, we studied a series
of thin films subjected to controlled and natural oxidation. As Cu and CuOx is
a system that is already known to be highly influenced by oxidation, this metal
was chosen to carry out this study. We investigated these samples using SP-FMR
in YIG/Pt(2)/CuOx(tCu) and X-ray absorption spectroscopy and concluded that
samples with natural oxidation of Cu exhibit more significant results than
those when the CuOx is obtained by reactive sputtering. In particular, samples
where the Cu layer is naturally oxidized exhibit a Cu2O-rich phase. Our
findings help to elucidate the mechanisms underlying the inverse orbital Hall
and inverse orbital Rashba-Edelstein-like effects. These insights indeed
contribute to the advancement of devices that rely on orbital-charge
conversion.",2402.00297v1
2002-01-23,Mechanical detection of FMR spectrum in a normally magnetized YIG disk,"The ferromagnetic resonance spectrum of a normally magnetized YIG disk, with
thickness of 4.75$\mu$m and radius of 80$\mu$m, is measured at room temperature
both by magnetic resonance force microscopy and by standard detection of the
microwave susceptibility. The comparison indicates that MRFM represents one of
the most potent means of obtaining the \emph{complete} FMR spectra of
micron-size samples. In the weak coupling regime, the measured data can be
quantitatively understood within the framework of the Damon and Eshbach model.",0201409v1
2007-11-10,Stability of Bose Einstein condensates of hot magnons in YIG,"We investigate the stability of the recently discovered room temperature
Bose-Einstein condensate (BEC) of magnons in Ytrrium Iron Garnet (YIG) films.
We show that magnon-magnon interactions depend strongly on the external field
orientation, and that the BEC in current experiments is actually metastable -
it only survives because of finite size effects, and because the BEC density is
very low. On the other hand a strong field applied perpendicular to the sample
plane leads to a repulsive magnon-magnon interaction; we predict that a
high-density magnon BEC can then be formed in this perpendicular field
geometry.",0711.1574v1
2014-12-03,Proximity-induced ferromagnetism in graphene revealed by anomalous Hall effect,"We demonstrate the anomalous Hall effect (AHE) in single-layer graphene
exchange-coupled to an atomically flat yttrium iron garnet (YIG) ferromagnetic
thin film. The anomalous Hall conductance has magnitude of ~0.09(2e2/h) at low
temperatures and is measurable up to ~ 300 K. Our observations indicate not
only proximity-induced ferromagnetism in graphene/YIG with large exchange
interaction, but also enhanced spin-orbit coupling which is believed to be
inherently weak in ideal graphene. The proximity-induced ferromagnetic order in
graphene can lead to novel transport phenomena such as the quantized AHE which
are potentially useful for spintronics.",1412.1521v1
2015-03-09,Magnetic spheres in microwave cavities,"We apply Mie scattering theory to study the interaction of magnetic spheres
with microwaves in cavities beyond the magnetostatic and rotating wave
approximations. We demonstrate that both strong and ultra-strong coupling can
be realized for a stand alone magnetic spheres made from yttrium iron garnet
(YIG), acting as an efficient microwave antenna. The eigenmodes of YIG spheres
with radii of the order mm's display distinct higher angular momentum character
that has been observed in experiments.",1503.02419v2
2017-07-12,Superconductivity Induced by Interfacial Coupling to Magnons,"We consider a thin normal metal sandwiched between two ferromagnetic
insulators. At the interfaces, the exchange coupling causes electrons within
the metal to interact with magnons in the insulators. This electron-magnon
interaction induces electron-electron interactions, which, in turn, can result
in p-wave superconductivity. In the weak-coupling limit, we solve the gap
equation numerically and estimate the critical temperature. In YIG-Au-YIG
trilayers, superconductivity sets in at temperatures somewhere in the interval
between 1 and 10 K. EuO-Au-EuO trilayers require a lower temperature, in the
range from 0.01 to 1 K.",1707.03754v1
2019-10-09,Thermally controlled confinement of spin wave field in a magnonic YIG waveguide,"Methods for detecting spin waves rely on electrodynamical coupling between
the spin wave dipolar field and an inductive probe. While this coupling is
usually treated as constant, in this work, we experimentally and theoretically
show that it is indeed temperature dependent. By measuring the spin wave
magnetic field as a function of temperature of, and distance to the sample, we
demonstrate that there is both a longitudinal and transversal confinement of
the field near the YIG-Air interface. Our results are relevant for spin wave
detection, in particular in the field of spin wave caloritronics",1910.04304v1
2020-09-22,From Chaotic Spin Dynamics to Non-collinear Spin Textures in YIG Nano-films by Spin Current Injection,"In this article I report about a numerical investigation of nonlinear spin
dynamics in a magnetic thin-film, made of Yttrium-Iron-Garnet (YIG). This film
is exposed to a small in-plane oriented magnetic field, and strong spin
currents. The rich variety of findings encompass dynamic regimes hosting
localized, non-propagating solitons, a turbulent chaotic regime, which
condenses into a quasi-static phase featuring a non-collinear spin texture.
Eventually, at largest spin current, a homogeneously switched state is
established.",2009.10628v1
2022-02-08,Modulation of Spin Seebeck Effect by Hydrogenation,"We demonstrate the modulation of spin Seebeck effect (SSE) by hydrogenation
in Pd/YIG bilayers. In the presence of 3% hydrogen gas, SSE voltage decreases
by more than 50% from the magnitude observed in pure Ar gas. The modulation of
the SSE voltage is reversible, but the recovery of the SSE voltage to the
prehydrogenation value takes a few days because of a long time constant of
hydrogen desorption. We also demonstrate that the spin Hall magnetoresistance
of the identical sample reduces significantly with hydrogen exposure,
supporting that the observed modulation of spin current signals originates from
hydrogenation of Pd/YIG.",2202.03774v1
2023-01-14,Quantum entanglement generation on magnons assisted with microwave cavities coupled to a superconducting qubit,"We present protocols to generate quantum entanglement on nonlocal magnons in
hybrid systems composed of yttrium iron garnet (YIG) spheres, microwave
cavities and a superconducting (SC) qubit. In the schemes, the YIGs are coupled
to respective microwave cavities in resonant way, and the SC qubit is placed at
the center of the cavities, which interacts with the cavities simultaneously.
By exchanging the virtual photon, the cavities can indirectly interact in the
far-detuning regime. Detailed protocols are presented to establish entanglement
for two, three and arbitrary $N$ magnons with reasonable fidelities.",2301.05820v1
2014-09-19,Study of strong photon-magnon coupling in a YIG-film split-ring resonant system,"By using the stripline Microwave Vector Network Analyzer Ferromagnetic
Resonance and Pulsed Inductive Microwave Magnetometry spectroscopy techniques,
we study a strong coupling regime of magnons to microwave photons in the planar
geometry of a lithographically formed split-ring resonator (SRR) loaded by a
single-crystal epitaxial yttrium-iron garnet (YIG) film. Strong anti-crossing
of the photon modes of SRR and of the magnon modes of the YIG film is observed
in the applied-magnetic-field resolved measurements. The coupling strength
extracted from the experimental data reaches 9 percent at 3 GHz.
  Theoretically, we propose an equivalent circuit model of an SRR loaded by a
magnetic film. This model follows from the results of our numerical simulations
of the microwave field structure of the SRR and of the magnetization dynamics
in the YIG film driven by the microwave currents in the SRR. The equivalent
circuit model is in good agreement with the experiment. It provides a simple
physical explanation of the process of mode anti-crossing.
  Our findings are important for future applications in microwave quantum
photonic devices as well as in magnetically tunable metamaterials exploiting
the strong coupling of magnons to microwave photons.",1409.5499v1
2015-03-25,Rigorous numerical study of strong microwave photon-magnon coupling in all-dielectric magnetic multilayers,"We demonstrate theoretically a strong local enhancement of the intensity of
the in-plane microwave magnetic field in multilayered structures made from a
magneto-insulating yttrium iron garnet (YIG) layer sandwiched between two
non-magnetic layers with a high dielectric constant matching that of YIG. The
enhancement is predicted for the excitation regime when the microwave magnetic
field is induced inside the multilayer by the transducer of a stripline
Broadband Ferromagnetic Resonance (BFMR) setup. By means of a rigorous
numerical solution of the Landau-Lifshitz-Gilbert equation consistently with
the Maxwell's equations, we investigate the magnetisation dynamics in the
multilayer. We reveal a strong photon-magnon coupling, which manifests itself
as anti-crossing of the ferromagnetic resonance (FMR) magnon mode supported by
the YIG layer and the electromagnetic resonance mode supported by the whole
multilayered structure. The frequency of the magnon mode depends on the
external static magnetic field, which in our case is applied tangentially to
the multilayer in the direction perpendicular to the microwave magnetic field
induced by the stripline of the BFMR setup. The frequency of the
electromagnetic mode is independent of the static magnetic field. Consequently,
the predicted photon-magnon coupling is sensitive to the applied magnetic field
and thus can be used in magnetically tuneable metamaterials based on
simultaneously negative permittivity and permeability achievable thanks to the
YIG layer. We also suggest that the predicted photon-magnon coupling may find
applications in microwave quantum information systems.",1503.07282v1
2015-12-24,Ultra-High Cooperativity Interactions between Magnons and Resonant Photons in a YIG sphere,"Resonant photon modes of a 5mm diameter YIG sphere loaded in a cylindrical
cavity in the 10-30GHz frequency range are characterised as a function of
applied DC magnetic field at millikelvin temperatures. The photon modes are
confined mainly to the sphere, and exhibited large mode filling factors in
comparison to previous experiments, allowing ultrastrong coupling with the
magnon spin wave resonances. The largest observed coupling between photons and
magnons is $2g/2\pi=7.11$ GHz for a 15.5 GHz mode, corresponding to a
cooperativity of $C=1.51\pm0.47\times10^7$. Complex modifications beyond a
simple multi-oscillator model, of the photon mode frequencies were observed
between 0 and 0.1 Tesla. Between 0.4 to 1 Tesla, degenerate resonant photon
modes were observed to interact with magnon spin wave resonances with different
couplings strengths, indicating time reversal symmetry breaking due to the
gyrotropic permeability of YIG. Bare dielectric resonator mode frequencies were
determined by detuning magnon modes to significantly higher frequencies with
strong magnetic fields. By comparing measured mode frequencies at 7 Tesla with
Finite Element modelling, a bare dielectric permittivity of $15.96\pm0.02$ of
the YIG crystal has been determined at about $20$ mK.",1512.07773v5
2016-01-21,Detection of spin pumping from YIG by spin-charge conversion in a Au/Ni$_{80}$Fe$_{20}$ spin-valve structure,"Many experiments have shown the detection of spin-currents driven by
radio-frequency spin pumping from yttrium iron garnet (YIG), by making use of
the inverse spin-Hall effect, which is present in materials with strong
spin-orbit coupling, such as Pt. Here we show that it is also possible to
directly detect the resonance-driven spin-current using Au/permalloy (Py,
Ni$_{80}$Fe$_{20}$) devices, where Py is used as a detector for the spins
pumped across the YIG/Au interface. This detection mechanism is equivalent to
the spin-current detection in metallic non-local spin-valve devices. By finite
element modeling we compare the pumped spin-current from a reference Pt strip
with the detected signals from the Au/Py devices. We find that for one series
of Au/Py devices the calculated spin pumping signals mostly match the
measurements, within 20%, whereas for a second series of devices additional
signals are present which are up to a factor 10 higher than the calculated
signals from spin pumping. We also identify contributions from thermoelectric
effects caused by the resonant (spin-related) and non-resonant heating of the
YIG. Thermocouples are used to investigate the presence of these thermal
effects and to quantify the magnitude of the Spin-(dependent-)Seebeck effect.
Several additional features are observed, which are also discussed.",1601.05605v1
2016-04-12,The effect of inserted NiO layer on spin-Hall magnetoresistance in Pt/NiO/YIG heterostructures,"We investigate the spin-current transport through antiferromagnetic insulator
(AFMI) by means of the spin-Hall magnetoressitance (SMR) over a wide
temperature range in Pt/NiO/Y$_3$Fe$_5$O$_{12}$ (Pt/NiO/YIG) heterostructures.
By inserting the AFMI NiO layer, the SMR dramatically decreases by decreasing
the temperature down to the antiferromagnetically ordered state of NiO, which
implies that the AFM order prevents rather than promotes the spin-current
transport. On the other hand, the magnetic proximity effect (MPE) on induced Pt
moments by YIG, which entangles with the spin-Hall effect (SHE) in Pt, can be
efficiently screened, and pure SMR can be derived by insertion of NiO. The dual
roles of the NiO insertion including efficiently blocking the MPE and
transporting the spin current from Pt to YIG are outstanding compared with
other antiferromagnetic (AFM) metal or nonmagnetic metal (NM).",1604.03272v2
2017-12-12,Microwave to optical photon conversion by means of travelling-wave magnons in YIG films,"In this work we study theoretically the efficiency of a travelling magnon
based microwave to optical photon converter for applications in Quantum
Information (QI). The converter employs an epitaxially grown yttrium iron
garnet (YIG) film as the medium for propagation of travelling magnons (spin
waves). The conversion is achieved through coupling of magnons to guided
optical modes of the film. The total microwave to optical photon conversion
efficiency is found to be larger than in a similar process employing a YIG
sphere by at least 4 orders of magnitude. By creating an optical resonator of a
large length from the film (such that the traveling magnon decays before
forming a standing wave over the resonator length) one will be able to further
increase the efficiency by several orders of magnitude, potentially reaching a
value similar to achieved with opto-mechanical resonators. Also, as a spin-off
result, it is shown that isolation of more that 20 dB with direct insertion
losses about 5 dBm can be achieved with YIG film based microwave isolators for
applications in Quantum Information.
  An important advantage of the suggested concept of the QI devices based on
travelling spin waves is a perfectly planar geometry and a possibility of
implementing a the device as a hybrid opto-microwave chip.",1712.04304v2
2018-02-09,Monocrystalline free standing 3D yttrium iron garnet magnon nano resonators,"Nano resonators in which mechanical vibrations and spin waves can be coupled
are an intriguing concept that can be used in quantum information processing to
transfer information between different states of excitation. Until now, the
fabrication of free standing magnetic nanostructures which host long lived spin
wave excitatons and may be suitable as mechanical resonators seemed elusive. We
demonstrate the fabrication of free standing monocrystalline yttrium iron
garnet (YIG) 3D nanoresonators with nearly ideal magnetic properties. The
freestanding 3D structures are obtained using a complex lithography process
including room temperature deposition and lift-off of amorphous YIG and
subsequent crystallization by annealing. The crystallization nucleates from the
substrate and propagates across the structure even around bends over distances
of several micrometers to form e.g. monocrystalline resonators as shown by
transmission electron microscopy. Spin wave excitations in individual
nanostructures are imaged by time resolved scanning Kerr microscopy. The narrow
linewidth of the magnetic excitations indicates a Gilbert damping constant of
only $\alpha = 2.6 \times 10^{-4}$ rivalling the best values obtained for
epitaxial YIG thin film material. The new fabrication process represents a leap
forward in magnonics and magnon mechanics as it provides 3D YIG structures of
unprecedented quality. At the same time it demonstrates a completely new route
towards the fabrication of free standing crystalline nano structures which may
be applicable also to other material systems.",1802.03176v2
2018-11-29,"Effect of YIG Nanoparticle Size and Clustering in Proximity-Induced Magnetism in Graphene/YIG Composite Probed with Magnetoimpedance Sensors: Towards Improved Functionality, Sensitivity and Proximity Detection","Proximity-induced magnetism (PIM) in graphene (Gr) adjacent to magnetic
specimen has raised great fundamental interests. The subject is under debate
and yet no application is proposed and granted. In this paper, toward
accomplishment of fundamental facts, we first explore the effect of particle
size and clustering in the PIM in Gr nanoplates (GNPs)/yttrium iron garnet
(YIG) magnetic nanoparticle (MNP) composite. Microscopic analyzes suggest that
fine MNPs distributed uniformly on the GNPs have higher saturation
magnetization due to the PIM in Gr. We propose that such magnetic plates can
thus be used to shield the stray field generated on the surface of magnetic
sensors and play a role as a magnetic lens to prevent the field emanating
outside the body of magnetic specimen. The GNPs/YIG composites are coated on a
magnetic ribbon and proposed for application in magneto-impedance (MI) sensors.
We show that such planar magnetic flakes enhance the MI response against the
external applied magnetic field significantly. The suggested application can be
furthermore developed toward bio-sensing and magnetic shielding in different
magnetic sensors and devices.",1811.12317v2
2018-12-23,Temperature dependence of the effective spin-mixing conductance probed with lateral non-local spin valves,"We report the temperature dependence of the effective spin-mixing conductance
between a normal metal (aluminium, Al) and a magnetic insulator
($\text{Y}_3\text{Fe}_5\text{O}_{12}$, YIG). Non-local spin valve devices,
using Al as the spin transport channel, were fabricated on top of YIG and
SiO$_2$ substrates. By comparing the spin relaxation lengths in the Al channel
on the two different substrates, we calculate the effective spin-mixing
conductance ($G_\text{s}$) to be $3.3\times10^{12}$~$\Omega^{-1}\text{m}^{-2}$
at 293~K for the Al/YIG interface. A decrease of up to 84\% in $G_\text{s}$ is
observed when the temperature ($T$) is decreased from 293~K to 4.2~K, with
$G_\text{s}$ scaling with $(T/T_\text{c})^{3/2}$. The real part of the
spin-mixing conductance ($G_\text{r}\approx 5.7\times10^{13}~
\Omega^{-1}\text{m}^{-2}$), calculated from the experimentally obtained
$G_\text{s}$, is found to be approximately independent of the temperature. We
evidence a hitherto unrecognized underestimation of $G_\text{r}$ extracted from
the modulation of the spin signal by rotating the magnetization direction of
YIG with respect to the spin accumulation direction in the Al channel, which is
found to be 50 times smaller than the calculated value.",1812.09766v1
2019-05-11,Giant Spin Seebeck Effect through an Interface Organic Semiconductor,"Interfacing an organic semiconductor C60 with a non-magnetic metallic thin
film (Cu or Pt) has created a novel heterostructure that is ferromagnetic at
ambient temperature, while its interface with a magnetic metal (Fe or Co) can
tune the anisotropic magnetic surface property of the material. Here, we
demonstrate that sandwiching C60 in between a magnetic insulator (Y3Fe5O12:
YIG) and a non-magnetic, strong spin-orbit metal (Pt) promotes highly efficient
spin current transport via the thermally driven spin Seebeck effect (SSE).
Experiments and first principles calculations consistently show that the
presence of C60 reduces significantly the conductivity mismatch between YIG and
Pt and the surface perpendicular magnetic anisotropy of YIG, giving rise to
enhanced spin mixing conductance across YIG/C60/Pt interfaces. As a result, a
600% increase in the SSE voltage (VLSSE) has been realized in YIG/C60/Pt
relative to YIG/Pt. Temperature-dependent SSE voltage measurements on
YIG/C60/Pt with varying C60 layer thicknesses also show an exponential increase
in VLSSE at low temperatures below 200 K, resembling the temperature evolution
of spin diffusion length of C60. Our study emphasizes the important roles of
the magnetic anisotropy and the spin diffusion length of the intermediate layer
in the SSE in YIG/C60/Pt structures, providing a new pathway for developing
novel spin-caloric materials.",1905.04555v1
2019-10-07,Chiral spin-wave velocities induced by all-garnet interfacial Dzyaloshinskii-Moriya interaction in ultrathin yttrium iron garnet films,"Spin waves can probe the Dzyaloshinskii-Moriya interaction (DMI) which gives
rise to topological spin textures, such as skyrmions. However, the DMI has not
yet been reported in yttrium iron garnet (YIG) with arguably the lowest damping
for spin waves. In this work, we experimentally evidence the interfacial DMI in
a 7~nm-thick YIG film by measuring the nonreciprocal spin wave propagation in
terms of frequency, amplitude and most importantly group velocities using all
electrical spin-wave spectroscopy. The velocities of propagating spin waves
show chirality among three vectors, i.e. the film normal direction, applied
field and spin-wave wavevector. By measuring the asymmetric group velocities,
we extract a DMI constant of 16~$\mu$J/m$^{2}$ which we independently confirm
by Brillouin light scattering. Thickness-dependent measurements reveal that the
DMI originates from the oxide interface between the YIG and garnet substrate.
The interfacial DMI discovered in the ultrathin YIG films is of key importance
for functional chiral magnonics as ultra-low spin-wave damping can be achieved.",1910.02599v2
2019-12-01,Differences in the magnon diffusion length for electrically and thermally driven magnon currents in Y$_3$Fe$_5$O$_{12}$,"Recent demonstration of efficient transport and manipulation of spin
information by magnon currents have opened exciting prospects for processing
information in devices. Magnon currents can be driven both electrically and
thermally, even in magnetic insulators, by applying charge currents in an
adjacent metal layer. Earlier reports in thin yttrium iron garnet (YIG) films
suggested that the diffusion length of magnons is independent on the biasing
method, but different values were obtained in thicker films. Here, we study the
magnon diffusion length for electrically and thermally driven magnon currents
in the linear regime in a 2-$\mu$m-thick YIG film as a function of temperature
and magnetic field. Our results show a decrease of the magnon diffusion length
with magnetic field for both biasing methods and at all temperatures from 5 to
300 K, indicating that sub-thermal magnons dominate the long-range transport.
Moreover, we demonstrate that the value of the magnon diffusion length depends
on the driving mechanism, suggesting that different non-equilibrium magnon
distributions are biased for each method. Finally, we demonstrate that the
magnon diffusion length for thermally driven magnon currents is independent of
the YIG thickness and material growth conditions, confirming that this quantity
is an intrinsic parameter of YIG.",1912.00490v2
2020-09-06,Enhancement of YIG$|$Pt spin conductance by local Joule annealing,"We report that Joule heating can be used to enhance the interfacial spin
conductivity between a metal and an oxide. We observe that local annealing of
the interface at about 550\,K by injecting large current densities
($>10^{12}\text{A/m}^{2}$) into a pristine 7\,nm thick Pt nanostrip evaporated
on top of yttrium iron garnet (YIG), can improve the spin transmission up to a
factor 3: a result of particular interest for interfacing ultra thin garnet
films where strong chemical etching of the surface has to be avoided. The
effect is confirmed by different methods: spin Hall magnetoresistance, spin
pumping and non-local spin transport. We use it to study the influence of the
YIG$|$Pt coupling on the non-linear spin transport properties. We find that the
cross-over current from a linear to a non-linear spin transport regime is
independent of this coupling, suggesting that the behavior of pure spin
currents circulating in the dielectric are mostly governed by the physical
properties of the bare YIG film beside the Pt nanostrip.",2009.02785v1
2021-04-19,Magnetic coupling in Y$_3$Fe$_5$O$_{12}$/Gd$_3$Fe$_5$O$_{12}$ heterostructures,"Ferrimagnetic Y$_3$Fe$_5$O$_{12}$ (YIG) is the prototypical material for
studying magnonic properties due to its exceptionally low damping. By
substituting the yttrium with other rare earth elements that have a net
magnetic moment, we can introduce an additional spin degree of freedom. Here,
we study the magnetic coupling in epitaxial
Y$_3$Fe$_5$O$_{12}$/Gd$_3$Fe$_5$O$_{12}$ (YIG/GIG) heterostructures grown by
pulsed laser deposition. From bulk sensitive magnetometry and surface sensitive
spin Seebeck effect (SSE) and spin Hall magnetoresistance (SMR) measurements,
we determine the alignment of the heterostructure magnetization through
temperature and external magnetic field. The ferromagnetic coupling between the
Fe sublattices of YIG and GIG dominates the overall behavior of the
heterostructures. Due to the temperature dependent gadolinium moment, a
magnetic compensation point of the total bilayer system can be identified. This
compensation point shifts to lower temperatures with increasing thickness of
YIG due the parallel alignment of the iron moments. We show that we can control
the magnetic properties of the heterostructures by tuning the thickness of the
individual layers, opening up a large playground for magnonic devices based on
coupled magnetic insulators. These devices could potentially control the magnon
transport analogously to electron transport in giant magnetoresistive devices.",2104.09592v1
2023-09-06,Strong magnon-magnon coupling in an ultralow damping all-magnetic-insulator heterostructure,"Magnetic insulators such as yttrium iron garnets (YIGs) are of paramount
importance for spin-wave or magnonic devices as their ultralow damping enables
ultralow power dissipation that is free of Joule heating, exotic magnon quantum
state, and coherent coupling to other wave excitations. Magnetic insulator
heterostructures bestow superior structural and magnetic properties and house
immense design space thanks to the strong and engineerable exchange interaction
between individual layers. To fully unleash their potential, realizing low
damping and strong exchange coupling simultaneously is critical, which often
requires high quality interface. Here, we show that such a demand is realized
in an all-insulator thulium iron garnet (TmIG)/YIG bilayer system. The ultralow
dissipation rates in both YIG and TmIG, along with their significant spin-spin
interaction at the interface, enable strong and coherent magnon-magnon coupling
with a benchmarking cooperativity value larger than the conventional
ferromagnetic metal-based heterostructures. The coupling strength can be tuned
by varying the magnetic insulator layer thickness and magnon modes, which is
consistent with analytical calculations and micromagnetic simulations. Our
results demonstrate TmIG/YIG as a novel platform for investigating hybrid
magnonic phenomena and open opportunities in magnon devices comprising
all-insulator heterostructures.",2309.03116v1
2023-09-16,Exploring orbital-charge conversion mediated by interfaces with copper through spin-orbital pumping,"We investigated how different materials affect the orbital-charge conversion
in heterostructures with the naturally oxidized cooper capping layer. When we
added a thin layer of $CuOx(3nm)$ onto yttrium iron garnet $(YIG)/W$ stacks, we
observed a significant reduction in the charge current signal measured by means
the spin pumping effect technique. This finding contrasts with the results of a
prior study conducted on YIG/Pt/CuOx, which reported the opposite effect. On
the other hand, when we added the same $CuOx(3nm)$ layer to $YIG/Ti(4nm)$
structures, there was not much change in the spin pumping signal. This occurred
because Ti does not generate much orbital current at the $Ti/CuOx$ interface,
unlike Pt, due to its weaker spin-orbit coupling. Interestingly, when we added
the $CuOx(3nm)$ layer to $SiO_{2}/Py(5nm)/Pt(4nm)$ structures, the spin pumping
signal increased. However, in $SiO_{2}/CuOx(3nm)/Pt(4nm)/Py(5nm)$ structures,
the signal decreased. Finally, we delve into a theoretical analysis of the spin
(orbital) Hall effect in YIG/Heavy-metal systems. These findings have the
potential to advance research in the innovative field of orbitronics and
contribute to the development of new technologies based on spin-orbital
conversion.",2309.08857v2
2023-12-22,Magnon-assisted magnetization reversal of Ni81Fe19 nanostripes on Y3Fe5O12 with different interfaces,"Magnetic bit writing by short-wave magnons without conversion to the
electrical domain is expected to be a game-changer for in-memory computing
architectures. Recently, the reversal of nanomagnets by propagating magnons was
demonstrated. However, experiments have not yet explored different wavelengths
and the nonlinear excitation regime of magnons required for computational
tasks. We report on the magnetization reversal of individual 20-nm-thick
Ni81Fe19 (Py) nanostripes integrated onto 113-nm-thick yttrium iron garnet
(YIG). We suppress direct interlayer exchange coupling by an intermediate layer
such as Cu and SiO2. Exciting magnons in YIG with wavelengths {\lambda} down to
148 nm we observe the reversal of the integrated ferromagnets in a small
opposing field of 14 mT. Magnons with a small wavelength of {\lambda} = 195 nm,
i.e., twice the width of the Py nanostripes, induced the reversal at an
unprecedentedly small spin precessional power of about 1 nW after propagating
over 15 {\mu}m in YIG. Considerations based on dynamic dipolar coupling explain
the observed wavelength dependence of magnon-induced reversal efficiency. For
an increased power the stripes reversed in an opposing field of only about 1
mT. Our findings are important for the practical implementation of nonvolatile
storage of broadband magnon signals in YIG by means of bistable nanomagnets
without the need of an appreciable global magnetic field.",2312.15107v1
2009-02-18,Theory of coherence in Bose-Einstein condensation phenomena in a microwave driven interacting magnon gas,"Strong experimental evidences of the formation of quasi-equilibrium
Bose-Einstein condensation (BEC) of magnons at room temperature in a film of
yttrium iron garnet (YIG) excited by microwave radiation have been recently
reported. Here we present a theory for the magnon gas driven by a microwave
field far out of equilibrium showing that the nonlinear magnetic interactions
create cooperative mechanisms for the onset of a phase transition leading to
the spontaneous generation of quantum coherence and magnetic dynamic order in a
macroscopic scale. The theory provides rigorous support for the formation of a
BEC of magnons in a YIG film magnetized in the plane. We show that the system
develops coherence only when the microwave driving power exceeds a threshold
value and that the theoretical result for the intensity of the Brillouin light
scattering from the BEC as a function of power agrees with the experimental
data. The theory also explains quantitatively experimental measurements of
microwave emission from the uniform mode generated by the confluence of BEC
magnon pairs in a YIG film when the driving power exceeds a critical value.",0902.3138v1
2012-06-28,Frequency and power dependence of spin-current emission by spin pumping in a thin film YIG/Pt system,"This paper presents the frequency dependence of the spin current emission in
a hybrid ferrimagnetic insulator/normal metal system. The system is based on a
ferrimagnetic insulating thin film of Yttrium Iron Garnet (YIG, 200 nm) grown
by liquid-phase-epitaxy (LPE) coupled with a normal metal with a strong
spin-orbit coupling (Pt, 15 nm). The YIG layer presents an isotropic behaviour
of the magnetization in the plane, a small linewidth, and a roughness lower
than 0.4 nm. Here we discuss how the voltage signal from the spin current
detector depends on the frequency [0.6 - 7 GHz], the microwave power, Pin, [1 -
70 mW], and the in-plane static magnetic field. A strong enhancement of the
spin current emission is observed at low frequencies, showing the appearance of
non-linear phenomena.",1206.6671v2
2013-07-10,"Scaling of spin Hall angle in 3d, 4d and 5d metals from Y3Fe5O12/metal spin pumping","Pure spin currents generated by spin pumping in ferromagnet/nonmagnet (FM/NM)
bilayers produce inverse spin Hall effect (ISHE) voltages in the NM, from which
spin pumping and transport characteristics of the NM can be extracted. Due to
its exceptionally low damping, Y3Fe5O12 (YIG) is an important and widely used
FM for microwave devices and ferromagnetic resonance (FMR) spin pumping. Here
we report systematic investigation of spin pumping from 20-nm thick YIG thin
films to a series of 3d, 4d and 5d normal metals (Cu, Ag, Ta, W, Pt and Au)
with various spin-orbit coupling strengths. From enhanced Gilbert damping
obtained from the frequency dependence of FMR linewidths and ISHE signals, the
spin Hall angles and YIG/NM interfacial spin mixing conductances are
quantitatively determined for these metals. The spin Hall angles largely vary
as the fourth power of the atomic number, corroborating the dominant role of
spin-orbit coupling across a broad range in the inverse spin Hall effect.",1307.2648v2
2013-08-01,Inverse Spin Hall Effect in nanometer-thick YIG/Pt system,"High quality nanometer-thick (20 nm, 7 nm and 4 nm) epitaxial YIG films have
been grown on GGG substrates using pulsed laser deposition. The Gilbert damping
coefficient for the 20 nm thick films is 2.3 x 10-4 which is the lowest value
reported for sub-micrometric thick films. We demonstrate Inverse spin Hall
effect (ISHE) detection of propagating spin waves using Pt. The amplitude and
the lineshape of the ISHE voltage correlate well to the increase of the Gilbert
damping when decreasing thickness of YIG. Spin Hall effect based
loss-compensation experiments have been conducted but no change in the
magnetization dynamics could be detected.",1308.0192v1
2013-09-09,Sub-microsecond fast temporal evolution of the spin Seebeck effect,"We present temporal evolution of the spin Seebeck effect in a YIG|Pt bilayer
system. Our findings reveal that this effect is a sub-microseconds fast
phenomenon governed by the temperature gradient and the thermal magnons
diffusion in the magnetic materials. A comparison of experimental results with
the thermal-driven magnon-diffusion model shows that the temporal behavior of
this effect depends on the time development of the temperature gradient in the
vicinity of the YIG|Pt interface. The effective thermal-magnon diffusion length
for YIG|Pt systems is estimated to be around 700nm.",1309.2164v1
2014-10-07,Y3Fe5O12 Spin Pumping for Quantitative Understanding of Pure Spin Transport and Spin Hall Effect in a Broad Range of Materials,"Using Y3Fe5O12 (YIG) thin films grown by our sputtering technique, we study
dynamic spin transport in nonmagnetic (NM), ferromagnetic (FM) and
antiferromagnetic (AF) materials by ferromagnetic resonance (FMR) spin pumping.
From both inverse spin Hall effect (ISHE) and damping enhancement, we determine
the spin mixing conductance and spin Hall angle in many metals. Surprisingly,
we observe robust spin conduction in AF insulators excited by an adjacent YIG
at resonance. This demonstrates that YIG spin pumping is a powerful and
versatile tool for understanding spin Hall physics, spin-orbit coupling (SOC),
and magnetization dynamics in a broad range of materials.",1410.1597v1
2014-10-22,Spin current generation from sputtered Y3Fe5O12 films,"Spin current injection from sputtered yttrium iron garnet (YIG) films into an
adjacent platinum layer has been investigated by means of the spin pumping and
the spin Seebeck effects. Films with a thickness of 83 and 96 nanometers were
fabricated by on-axis magnetron rf sputtering at room temperature and
subsequent post-annealing. From the frequency dependence of the ferromagnetic
resonance linewidth, the damping constant has been estimated to be
$(7.0\pm1.0)\times 10^{-4}$. Magnitudes of the spin current generated by the
spin pumping and the spin Seebeck effect are of the same order as values for
YIG films prepared by liquid phase epitaxy. The efficient spin current
injection can be ascribed to a good YIG|Pt interface, which is confirmed by the
large spin-mixing conductance $(2.0\pm0.2)\times 10^{18}$ m$^{-2}$.",1410.5987v1
2014-12-07,Magnonic band gaps in YIG based magnonic crystals: array of grooves versus array of metallic stripes,"The magnonic band gaps of the two types of planar one-dimensional magnonic
crystals comprised of the periodic array of the metallic stripes on yttrium
iron garnet (YIG) film and YIG film with an array of grooves was analyzed
experimentally and theoretically. In such periodic magnetic structures the
propagating magnetostatic surface spin waves were excited and detected by
microstripe transducers with vector network analyzer and by Brillouin light
scattering spectroscopy. Properties of the magnonic band gaps were explained
with the help of the finite element calculations. The important influence of
the nonreciprocal properties of the spin wave dispersion induced by metallic
stripes on the magnonic band gap width and its dependence on the external
magnetic field has been shown. The usefulness of both types of the magnonic
crystals for potential applications and possibility for miniaturization are
discussed.",1412.2367v2
2014-12-22,Surface sensitivity of the spin Seebeck effect,"We have investigated the influence of the interface quality on the spin
Seebeck effect (SSE) of the bilayer system yttrium iron garnet (YIG) - platinum
(Pt). The magnitude and shape of the SSE is strongly influenced by mechanical
treatment of the YIG single crystal surface. We observe that the saturation
magnetic field H_{sat} for the SSE signal increases from 55.3 mT to 72.8 mT
with mechanical treatment. The change in the magnitude of H_{sat} can be
attributed to the presence of a perpendicular magnetic anisotropy due to the
treatment induced surface strain or shape anisotropy in the Pt/YIG system. Our
results show that the SSE is a powerful tool to investigate magnetic anisotropy
at the interface.",1412.7712v1
2015-02-18,Spectral shape deformation in inverse spin Hall voltage in Y3Fe5O12|Pt bilayers at high microwave power levels,"We report on the deformation of microwave absorption spectra and of the
inverse spin Hall voltage signals in thin film bilayers of yttrium iron garnet
(YIG) and platinum at high microwave power levels in a 9.45-GHz TE011 cavity.
As the microwave power increases from 0.15 to 200 mW, the resonance field
shifts to higher values, and the initially Lorentzian spectra of the microwave
absorption intensity as well as the inverse spin Hall voltage signals become
asymmetric. The contributions from opening of the magnetization precession cone
and heating of YIG cannot well reproduce the data. Control measurements of
inverse spin Hall voltages on thin-film YIG|Pt systems with a range of line
widths underscore the role of spin-wave excitations in spectral deformation.",1502.05198v1
2015-02-13,Spin-current injection and detection in strongly correlated organic conductor,"Spin-current injection into an organic semiconductor
$\rm{\kappa\text{-}(BEDT\text{-}TTF)_2Cu[N(CN)_2]Br}$ film induced by the spin
pumping from an yttrium iron garnet (YIG) film. When magnetization dynamics in
the YIG film is excited by ferromagnetic or spin-wave resonance, a voltage
signal was found to appear in the
$\rm{\kappa\text{-}(BEDT\text{-}TTF)_2Cu[N(CN)_2]Br}$ film.
Magnetic-field-angle dependence measurements indicate that the voltage signal
is governed by the inverse spin Hall effect in
$\rm{\kappa\text{-}(BEDT\text{-}TTF)_2Cu[N(CN)_2]Br}$. We found that the
voltage signal in the $\rm{\kappa\text{-}(BEDT\text{-}TTF)_2Cu[N(CN)_2]Br}$/YIG
system is critically suppressed around 80 K, around which magnetic and/or glass
transitions occur, implying that the efficiency of the spin-current injection
is suppressed by fluctuations which critically enhanced near the transitions.",1502.05244v1
2015-04-03,The effect of the magnon dispersion on the longitudinal spin Seebeck effect in yttrium iron garnets (YIG),"We study the temperature dependence of the longitudinal spin-Seebeck effect
(LSSE) in a yttrium iron garnet Y3Fe5O12 (YIG) / Pt system for samples of
different thicknesses. In this system, the thermal spin torque is
magnon-driven. The LSSE signal peaks at a specific temperature that depends on
the YIG sample thickness. We also observe freeze-out of the LSSE signal at high
magnetic fields, which we attribute to the opening of an energy gap in the
magnon dispersion. We observe partial freeze-out of the LSSE signal even at
room temperature, where kBT is much larger than the gap. This suggests that a
subset of the magnon population with an energy below kB x TC (TC about 40 K)
contribute disproportionately to the LSSE; at temperatures below TC, we label
these magnons subthermal magnons. The T-dependence of the LSSE at temperatures
below the maximum is interpreted in terms of a new empirical model that
ascribes most of the temperature dependence to that of the thermally driven
magnon flux.",1504.00895v1
2015-09-14,Antiferromagnonic Spin Transport from Y$_3$Fe$_5$O$_{12}$ into NiO,"We observe highly efficient dynamic spin injection from Y$_3$Fe$_5$O$_{12}$
(YIG) into NiO, an antiferromagnetic (AF) insulator, via strong coupling, and
robust spin propagation in NiO up to 100-nm thickness mediated by its AF spin
correlations. Strikingly, the insertion of a thin NiO layer between YIG and Pt
significantly enhances the spin currents driven into Pt, suggesting
exceptionally high spin transfer efficiency at both YIG/NiO and NiO/Pt
interfaces. This offers a powerful platform for studying AF spin pumping and AF
dynamics as well as for exploration of spin manipulation in tailored structures
comprising metallic and insulating ferromagnets, antiferromagnets and
nonmagnetic materials.",1509.04337v1
2016-04-13,Magnon spin transport driven by the magnon chemical potential in a magnetic insulator,"We develop a linear-response transport theory of diffusive spin and heat
transport by magnons in magnetic insulators with metallic contacts. The magnons
are described by a position dependent temperature and chemical potential that
are governed by diffusion equations with characteristic relaxation lengths.
Proceeding from a linearized Boltzmann equation, we derive expressions for
length scales and transport coefficients. For yttrium iron garnet (YIG) at room
temperature we find that long-range transport is dominated by the magnon
chemical potential. We compare the model's results with recent experiments on
YIG with Pt contacts [L.J. Cornelissen, et al., Nat. Phys. 11, 1022 (2015)] and
extract a magnon spin conductivity of $\sigma_{m}=5\times10^{5}$ S/m. Our
results for the spin Seebeck coefficient in YIG agree with published
experiments. We conclude that the magnon chemical potential is an essential
ingredient for energy and spin transport in magnetic insulators.",1604.03706v1
2016-04-17,Interface electronic structure at the topological insulator - ferrimagnetic insulator junction,"An interface electron state at the junction between a three-dimensional
topological insulator (TI) film of Bi2Se3 and a ferrimagnetic insulator film of
Y3Fe5O12 (YIG) was investigated by measurements of angle-resolved photoelectron
spectroscopy and X-ray absorption magnetic circular dichroism (XMCD). The
surface state of the Bi2Se3 film was directly observed and localized 3d spin
states of the Fe3+ state in the YIG film were confirmed. The proximity effect
is likely described in terms of the exchange interaction between the localized
Fe 3d electrons in the YIG film and delocalized electrons of the surface and
bulk states in the Bi2Se3 film. The Curie temperature (TC) may be increased by
reducing the amount of the interface Fe2+ ions with opposite spin direction
observable as a pre-edge in the XMCD spectra.",1604.04869v1
2016-05-27,Combined Brillouin light scattering and microwave absorption study of magnon-photon coupling in a split-ring resonator/YIG film system,"Microfocused Brillouin light scattering (BLS) and microwave absorption (MA)
are used to study magnon-photon coupling in a system consisting of a split-ring
microwave resonator and a yttrium iron garnet (YIG) film. The split-ring
resonantor is defined by optical lithography and loaded with a 1 $\mu$m-thick
YIG film grown by liquid phase epitaxy. BLS and MA spectra of the hybrid system
are simultaneously recorded as a function of the applied magnetic field
magnitude and microwave excitation frequency. Strong coupling of the magnon and
photon modes is found with a coupling strength of $g_\text{eff}/2 \pi = 63$
MHz. The combined BLS and MA data allows to study the continuous transition of
the hybridized modes from a purely magnonic to a purely photonic mode by
varying the applied magnetic field and microwave frequency. Furthermore, the
BLS data represent an up-conversion of the microwave frequency coupling to
optical frequencies.",1605.08531v1
2016-07-08,Control of magnon-photon coupling strength in a planar resonator/YIG thin film configuration,"A systematic study of the coupling at room temperature between ferromagnetic
resonance (FMR) and a planar resonator is presented. The chosen magnetic
material is a ferrimagnetic insulator (Yttrium Iron Garnet: YIG) which is
positioned on top of a stop band (notch) filter based on a stub line
capacitively coupled to a 50 $\Omega$ microstrip line resonating at 4.731 GHz.
Control of the magnon-photon coupling strength is discussed in terms of the
microwave excitation configuration and the YIG thickness from 0.2 to 41 $\mu$m.
From the latter dependence, we extract a single spin-photon coupling of
g$_{0}$/2$\pi$=162$\pm$6 mHz and a maximum of an effective coupling of 290 MHz.",1607.02358v3
2016-07-25,Damping of parametrically excited magnons in the presence of the longitudinal spin Seebeck effect,"The impact of the longitudinal spin Seebeck effect (LSSE) on the magnon
damping in magnetic-insulator/nonmagnetic-metal bilayers was recently discussed
in several reports. However, results of those experiments can be blurred by
multimode excitation within the measured linewidth. In order to avoid possible
intermodal interference, we investigated the damping of a single magnon group
in a platinum covered Yttrium Iron Garnet (YIG) film by measurement of the
threshold of its parametric excitation. Both dipolar and exchange spin-wave
branches were probed. It turned out that the LSSE-related modification of
spin-wave damping in a micrometer-thick YIG film is too weak to be observed in
the entire range of experimentally accessible wavevectors. At the same time,
the change in the mean temperature of the YIG layer, which can appear by
applying a temperature gradient, strongly modifies the damping value.",1607.07274v1
2016-09-26,Magnon Kerr effect in a strongly coupled cavity-magnon system,"We experimentally demonstrate magnon Kerr effect in a cavity-magnon system,
where magnons in a small yttrium iron garnet (YIG) sphere are strongly but
dispersively coupled to the photons in a three-dimensional cavity. When the YIG
sphere is pumped to generate considerable magnons, the Kerr effect yields a
perceptible shift of the cavity's central frequency and more appreciable shifts
of the magnon modes. We derive an analytical relation between the magnon
frequency shift and the drive power for the uniformly magnetized YIG sphere and
find that it agrees very well with the experimental results of the Kittel mode.
Our study paves the way to explore nonlinear effects in the cavity-magnon
system.",1609.07891v2
2016-09-24,Optical manipulation of a magnon-photon hybrid system,"We demonstrate an all-optical method for manipulating the magnetization in a
1-mm YIG (yttrium-iron-garnet) sphere placed in a $\sim0.17\,$T uniform
magnetic field. An harmonic of the frequency comb delivered by a multi-GHz
infrared laser source is tuned to the Larmor frequency of the YIG sphere to
drive magnetization oscillations, which in turn give rise to a radiation field
used to thoroughly investigate the phenomenon. The radiation damping issue that
occurs at high frequency and in the presence of highly magnetizated materials,
has been overcome by exploiting magnon-photon strong coupling regime in
microwave cavities. Our findings demonstrate an effective technique for
ultrafast control of the magnetization vector in optomagnetic materials via
polarization rotation and intensity modulation of an incident laser beam. We
eventually get a second-order susceptibility value of $\sim10^{-7}$ cm$^2$/MW
for single crystal YIG.",1609.08147v1
2016-10-27,Spin-wave propagation in ultra-thin YIG based waveguides,"Spin-wave propagation in an assembly of microfabricated 20 nm thick, 2.5
{\mu}m wide Yttrium Iron Garnet (YIG) waveguides is studied using propagating
spin-wave spectroscopy (PSWS) and phase resolved micro-focused Brillouin Light
Scattering ({\mu}-BLS) spectroscopy. We show that spin-wave propagation in 50
parallel waveguides is robust against microfabrication induced imperfections.
Spin-wave propagation parameters are studied in a wide range of excitation
frequencies for the Damon-Eshbach (DE) configuration. As expected from its low
damping, YIG allows the propagation of spin waves over long distances (the
attenuation lengths is 25 {\mu}m at \mu$_{0}$H = 45 mT). Direct mapping of spin
waves by {\mu}-BLS allows us to reconstruct the spin-wave dispersion relation
and to confirm the multi-mode propagation in the waveguides, glimpsed by
propagating spin-wave spectroscopy.",1610.08756v1
2016-12-06,Increased low-temperature damping in yttrium iron garnet thin films,"We report measurements of the frequency and temperature dependence of
ferromagnetic resonance (FMR) for a 15-nm-thick yttrium iron garnet (YIG) film
grown by off-axis sputtering. Although the FMR linewidth is narrow at room
temperature (corresponding to a damping coefficient $\alpha$ = (9.0 $\pm$ 0.2)
$\times 10^{-4}$), comparable to previous results for high-quality YIG films of
similar thickness, the linewidth increases strongly at low temperatures, by a
factor of almost 30. This increase cannot be explained as due to two-magnon
scattering from defects at the sample interfaces. We argue that the increased
low-temperature linewidth is due to impurity relaxation mechanisms that have
been investigated previously in bulk YIG samples. We suggest that the
low-temperature linewidth is a useful figure of merit to guide the optimization
of thin-film growth protocols because it is a particularly sensitive indicator
of impurities.",1612.01954v1
2016-12-24,Concomitant enhancement of longitudinal spin Seebeck effect with thermal conductivity,"We report a simultaneous measurement of a longitudinal spin Seebeck effect
(LSSE) and thermal conductivity in a Pt/${\rm Y_{3}Fe_{5}O_{12}}$ (YIG)/Pt
system in a temperature range from 10 to 300 K. By directly monitoring the
temperature difference in the system, we excluded thermal artifacts in the LSSE
measurements. It is found that both the LSSE signal and the thermal
conductivity of YIG exhibit sharp peaks at the same temperature, differently
from previous reports. The maximum LSSE coefficient is found to be
$S{\rm_{LSSE}}>10\ \mu{\rm V/K}$, one-order-of magnitude greater than the
previously reported values. The concomitant enhancement of the LSSE and thermal
conductivity of YIG suggests the strong correlation between magnon and phonon
transport in the LSSE.",1612.08142v1
2017-01-19,Separation of inverse spin Hall effect and anomalous Nernst effect in ferromagnetic metals,"Inverse spin Hall effect (ISHE) in ferromagnetic metals (FM) can also be used
to detect the spin current generated by longitudinal spin Seebeck effect in a
ferromagnetic insulator YIG. However, anomalous Nernst effect(ANE) in FM itself
always mixes in the thermal voltage. In this work, the exchange bias structure
(NiFe/IrMn)is employed to separate these two effects. The exchange bias
structure provides a shift field to NiFe, which can separate the magnetization
of NiFe from that of YIG in M-H loops. As a result, the ISHE related to
magnetization of YIG and the ANE related to the magnetization of NiFe can be
separated as well. By comparison with Pt, a relative spin Hall angle of NiFe
(0.87) is obtained, which results from the partially filled 3d orbits and the
ferromagnetic order. This work puts forward a practical method to use the ISHE
in ferromagnetic metals towards future spintronic applications.",1701.05320v1
2017-03-16,All-Angle Collimation for Spin Waves,"We studied the effect of collimation for monochromatic beams of spin waves,
resulting from the refraction at the interface separating two magnetic
half-planes. The collimation was observed in broad range of the angles of
ncidence for homogenous Co and Py half-planes, due to significant intrinsic
anisotropy of spin wave propagation in these materials. The effect exists for
the sample saturated by in plane magnetic field tangential to the interface.
The collimation for all possible angles of incidence was found in the system
where the incident spin wave is refracted on the interface between homogeneous
and periodically patterned layers of YIG. The refraction was investigated by
the analysis of isofrequency dispersion contours of both pairs materials, i.e.,
uniform YIG/patterned YIG and Co/Py, which are calculated with the aid of the
plane wave method. Besides, the refraction in Co/Py system was studied using
micromagnetic simulations.",1703.05548v1
2017-04-10,Patterned growth of crystalline Y$_{3}$Fe$_{5}$O$_{12}$ nanostructures with engineered magnetic shape anisotropy,"We demonstrate patterned growth of epitaxial yttrium iron garnet (YIG) thin
films using lithographically defined templates on gadolinium gallium garnet
(GGG) substrates. The fabricated YIG nanostructures yield the desired
crystallographic orientation, excellent surface morphology, and narrow
ferromagnetic resonance (FMR) linewidth (~ 4 Oe). Shape-induced magnetic
anisotropy is clearly observed in a patterned array of nanobars engineered to
exhibit the larger coercivity (40 Oe) compared with that of continuous films.
Both hysteresis loop and angle-dependent FMR spectra measurements indicate that
the easy axis aligns along the longitudinal direction of the nanobars, with an
effective anisotropy field of 195 Oe. Our work overcomes difficulties in
patterning YIG thin films and provides an effective means to control their
magnetic properties and magnetic bias conditions.",1704.03056v2
2017-06-06,Observation of spin superfluidity: YIG magnetic films and beyond,"From topology of the order parameter of the magnon condensate observed in
yttrium-iron-garnet (YIG) magnetic films one must not expect energetic barriers
making spin supercurrents metastable. But we show that some barriers of
dynamical origin are possible nevertheless until the gradient of the phase
(angle of spin precession) does not exceed the critical value (analog of the
Landau critical velocity in superfluids). On the other hand, recently published
claims of experimental detection of spin superfluidity in YIG films and
antiferromagnets are not justified, and spin superfluidity in magnetically
ordered solids has not yet been experimentally confirmed.",1706.01932v2
2017-06-27,Evidence for the role of the magnon energy relaxation length in the Spin Seebeck Effect,"Temperature-dependent spin-Seebeck effect data on Pt|YIG
(Y$_3$Fe$_5$O$_{12}$)|GGG (Gd$_3$Ga$_5$O$_{12}$) are reported for YIG films of
various thicknesses. The effect is reported as a spin-Seebeck resistivity
(SSR), the inverse spin-Hall field divided by the heat flux, to circumvent
uncertainties about temperature gradients inside the films. The SSR is a
non-monotonic function of YIG thickness. A diffusive model for magnon transport
demonstrates how these data give evidence for the existence of two distinct
length scales in thermal spin transport, a spin diffusion length and a magnon
energy relaxation length.",1706.09021v2
2017-08-02,Strongly exchange-coupled and surface-state-modulated magnetization dynamics in Bi2Se3/YIG heterostructures,"We report strong interfacial exchange coupling in Bi2Se3/yttrium iron garnet
(YIG) bilayers manifested as large in-plane interfacial magnetic anisotropy
(IMA) and enhancement of damping probed by ferromagnetic resonance (FMR). The
IMA and spin mixing conductance reached a maximum when Bi2Se3 was around 6
quintuple-layer (QL) thick. The unconventional Bi2Se3 thickness dependence of
the IMA and spin mixing conductance are correlated with the evolution of
surface band structure of Bi2Se3, indicating that topological surface states
play an important role in the magnetization dynamics of YIG.
Temperature-dependent FMR of Bi2Se3/YIG revealed signatures of magnetic
proximity effect of $T_c$ as high as 180 K, and an effective field parallel to
the YIG magnetization direction at low temperature. Our study sheds light on
the effects of topological insulators on magnetization dynamics, essential for
development of TI-based spintronic devices.",1708.00593v1
2017-09-26,Magnetic-field-induced suppression of spin Peltier effect in Pt/${\rm Y_{3}Fe_{5}O_{12}}$ system at room temperature,"We report the observation of magnetic-field-induced suppression of the spin
Peltier effect (SPE) in a junction of a paramagnetic metal Pt and a
ferrimagnetic insulator ${\rm Y_{3}Fe_{5}O_{12}}$ (YIG) at room temperature.
For driving the SPE, spin currents are generated via the spin Hall effect from
applied charge currents in the Pt layer, and injected into the adjacent thick
YIG film. The resultant temperature modulation is detected by a commonly-used
thermocouple attached to the Pt/YIG junction. The output of the thermocouple
shows sign reversal when the magnetization is reversed and linearly increases
with the applied current, demonstrating the detection of the SPE signal. We
found that the SPE signal decreases with the magnetic field. The observed
suppression rate was found to be comparable to that of the spin Seebeck effect
(SSE), suggesting the dominant and similar contribution of the low-energy
magnons in the SPE as in the SSE.",1709.08997v1
2017-10-07,Magnon-phonon relaxation in yttrium iron garnet from first principles,"We combine the theoretical method of calculating spin wave excitation with
the finite-temperature modeling and calculate the magnon-phonon relaxation time
in the technologically important material Yttrium iron garnet (YIG) from first
principles. The finite lifetime of magnon excitation is found to arise from the
fluctuation of the exchange interaction of magnetic atoms in YIG. At room
temperature, the magnon spectra have significant broadening that is used to
extract the magnon-phonon relaxation time quantitatively. The latter is a
phenomenological parameter of great importance in YIG-based spintronics
research. We find that the magnon-phonon relaxation time for the optical magnon
is a constant while that for the acoustic magnon is proportional to $1/k^2$ in
the long-wavelength regime.",1710.02647v1
2017-10-11,Approaching quantum anomalous Hall effect in proximity-coupled YIG/graphene/h-BN sandwich structure,"Quantum anomalous Hall state is expected to emerge in Dirac electron systems
such as graphene under both sufficiently strong exchange and spin-orbit
interactions. In pristine graphene, neither interaction exists; however, both
interactions can be acquired by coupling graphene to a magnetic insulator (MI)
as revealed by the anomalous Hall effect. Here, we show enhanced magnetic
proximity coupling by sandwiching graphene between a ferrimagnetic insulator
yttrium iron garnet (YIG) and hexagonal-boron nitride (h-BN) which also serves
as a top gate dielectric. By sweeping the top-gate voltage, we observe Fermi
level-dependent anomalous Hall conductance. As the Dirac point is approached
from both electron and hole sides, the anomalous Hall conductance reaches 1/4
of the quantum anomalous Hall conductance 2e2/h. The exchange coupling strength
is determined to be as high as 27 meV from the transition temperature of the
induced magnetic phase. YIG/graphene/h-BN is an excellent heterostructure for
demonstrating proximity-induced interactions in two-dimensional electron
systems.",1710.04179v1
2018-02-12,Spin-orbit torque and spin pumping in YIG/Pt with interfacial insertion layers,"We experimentally investigate spin-orbit torque and spin pumping in
Y$_3$Fe$_5$O$_{12}$(YIG)/Pt bilayers with ultrathin insertion layers at the
interface. An insertion layer of Cu suppresses both spin-orbit torque and spin
pumping, whereas an insertion layer of Ni$_{80}$Fe$_{20}$ (permalloy, Py)
enhances them, in a quantitatively consistent manner with the reciprocity of
the two spin transmission processes. However, we observe a large enhancement of
Gilbert damping with the insertion of Py that cannot be accounted for solely by
spin pumping, suggesting significant spin-memory loss due to the interfacial
magnetic layer. Our findings indicate that the magnetization at the YIG-metal
interface strongly influences the transmission and depolarization of pure spin
current.",1802.03865v3
2018-07-23,Bias dependent spin injection into graphene on YIG through bilayer hBN tunnel barriers,"We study the spin injection efficiency into single and bilayer graphene on
the ferrimagnetic insulator Yttrium-Iron-Garnet (YIG) through an exfoliated
tunnel barrier of bilayer hexagonal boron nitride (hBN). The contacts of two
samples yield a resistance-area product between 5 and 30 k$\Omega\mu$m$^2$.
Depending on an applied DC bias current, the magnitude of the non-local spin
signal can be increased or suppressed below the noise level. The spin injection
efficiency reaches values from -60% to +25%. The results are confirmed with
both spin valve and spin precession measurements. The proximity induced
exchange field is found in sample A to be (85 $\pm$ 30) mT and in sample B
close to the detection limit. Our results show that the exceptional spin
injection properties of bilayer hBN tunnel barriers reported by Gurram et al.
are not limited to fully encapsulated graphene systems but are also valid in
graphene/YIG devices. This further emphasizes the versatility of bilayer hBN as
an efficient and reliable tunnel barrier for graphene spintronics.",1807.08481v1
2018-10-11,"Propagating spin waves in nanometer-thick yttrium iron garnet films: Dependence on wave vector, magnetic field strength and angle","We present a comprehensive investigation of propagating spin waves in
nanometer-thick yttrium iron garnet (YIG) films. We use broadband spin-wave
spectroscopy with integrated coplanar waveguides (CPWs) and microstrip antennas
on top of continuous and patterned YIG films to characterize spin waves with
wave vectors up to 10 rad/$\mu$m. All films are grown by pulsed laser
deposition. From spin-wave transmission spectra, parameters such as the Gilbert
damping constant, spin-wave dispersion relation, group velocity, relaxation
time, and decay length are derived and their dependence on magnetic bias field
strength and angle is systematically gauged. For a 40-nm-thick YIG film, we
obtain a damping constant of $3.5 \times 10^{-4}$ and a maximum decay length of
1.2 mm. Our experiments reveal a strong variation of spin-wave parameters with
magnetic bias field and wave vector. Spin-wave properties change considerably
up to a magnetic bias field of about 30 mT and above a field angle of
$\theta_{H} = 20^{\circ}$, where $\theta_{H} = 0^{\circ}$ corresponds to the
Damon-Eshbach configuration.",1810.04973v1
2018-11-14,Anomalous Hall-like transverse magnetoresistance in Au thin films on Y$_3$Fe$_5$O$_{12}$,"Anomalous Hall-like signals in platinum in contact with magnetic insulators
are common observations that could be explained by either proximity
magnetization or spin Hall magnetoresistance. In this work, longitudinal and
transverse magnetoresistances are measured in a pure gold thin film on the
ferrimagnetic insulator Y$_3$Fe$_5$O$_{12}$ (Yttrium Iron Garnet, YIG). We show
that both the longitudinal and transverse magnetoresistances have
quantitatively consistent scaling in YIG/Au and in a YIG/Pt reference system
when applying the Spin Hall magnetoresistance framework. No contribution of an
anomalous Hall effect due to the magnetic proximity effect is evident.",1811.05848v1
2019-01-15,"SiC-YiG X band quantum sensor for sensitive surface paramagnetic resonance applied to chemistry, biology, physics","Here I present the SiC-YiG Quantum Sensor, allowing electron paramagnetic
resonance (EPR) studies of monolayer or few nanometers thick chemical,
biological or physical samples located on the sensor surface. It contains two
parts, a 4H-SiC substrate with many paramagnetic silicon vacancies (V2) located
below its surface, and YIG ferrimagnetic nanostripes. Spins sensing properties
are based on optically detected double electron-electron spin resonance under
the strong magnetic field gradient of nanostripes. Here I describe fabrication,
magnetic, optical and spins sensing properties of this sensor. I show that the
target spins sensitivity is at least five orders of magnitude larger than the
one of standard X band EPR spectrometer, for which it constitutes, combined
with a fiber bundle, a powerful upgrade for sensitive surface EPR. This sensor
can determine the target spins planes EPR spectrum, their positions with a
nanoscale precision of +/- 1 nm, and their 2D concentration down to
1/(20nm.20nm).",1901.05073v1
2019-01-17,Spin transport parameters of NbN thin films characterised by spin pumping experiments,"We present measurements of ferromagnetic-resonance - driven spin pumping and
inverse spin-Hall effect in NbN/Y3Fe5O12 (YIG) bilayers. A clear enhancement of
the (effective) Gilbert damping constant of the thin-film YIG was observed due
to the presence of the NbN spin sink. By varying the NbN thickness and
employing spin-diffusion theory, we have estimated the room temperature values
of the spin diffusion length and the spin Hall angle in NbN to be 14 nm and
-1.1 10-2, respectively. Furthermore, we have determined the spin-mixing
conductance of the NbN/YIG interface to be 10 nm-2. The experimental
quantification of these spin transport parameters is an important step towards
the development of superconducting spintronic devices involving NbN thin films.",1901.05753v1
2018-12-12,Substrate induced magnetic anisotropies and magneto-optical response in YIG nanosized epitaxial films on NdGG(111),"Nanosized Y3Fe5O12 epitaxial films have been grown on Nd3Ga5O12 substrates
using laser molecular beam epitaxy method. Magneto-optical polar Kerr effect,
ferromagnetic resonance and spin wave propagation measurements show that the
stress-related anisotropy field has an opposite sign, compared to that in the
YIG/GGG systems. This leads to a considerable decrease of the effective
magnetization that opens a perspective to get YIG films with perpendicular
magnetization for utilizing forward volume spin waves. Longitudinal
magnetooptical Kerr effect magnetometry reveals a large contribution of
quadratic in magnetization terms into dielectric permittivity tensor at optical
frequencies. This effect strongly increases with temperature decrease and is
explained by magnetization of the interface Nd3+ ions that are exchange coupled
to the Fe3+ ions.",1901.10800v1
2019-03-21,Room temperature and low-field resonant enhancement of spin Seebeck effect in partially compensated magnets,"Resonant enhancement of spin Seebeck effect (SSE) due to phonons was recently
discovered in Y3Fe5O12 (YIG). This effect is explained by hybridization between
the magnon and phonon dispersions. However, this effect was observed at low
temperatures and high magnetic fields, limiting the scope for applications.
Here we report observation of phonon-resonant enhancement of SSE at room
temperature and low magnetic field. We observed in Lu2BiFe4GaO12 and
enhancement 700 % greater than that in a YIG film and at very low magnetic
fields around 10-1 T, almost one order of magnitude lower than that of YIG. The
result can be explained by the change in the magnon dispersion induced by
magnetic compensation due to the presence of non-magnetic ion substitutions.
Our study provides a way to tune the magnon response in a crystal by chemical
doping with potential applications for spintronic devices.",1903.09007v1
2019-05-02,Anomalous spin Hall angle of a metallic ferromagnet determined by a multiterminal spin injection/detection device,"We report on the determination of the anomalous spin Hall angle in the
ferromagnetic metal alloy cobalt-iron (Co$_{25}$Fe$_{75}$, CoFe). This is
accomplished by measuring the spin injection/detection efficiency in a
multiterminal device with nanowires of platinum (Pt) and CoFe deposited onto
the magnetic insulator yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$, YIG). Applying
a spin-resistor model to our multiterminal spin transport data, we determine
the magnon conductivity in YIG, the spin conductance at the YIG/CoFe interface
and finally the anomalous spin Hall angle of CoFe as a function of its spin
diffusion length in a single device. Our experiments clearly reveal a negative
anomalous spin Hall angle of the ferromagnetic metal CoFe, but a vanishing
ordinary spin Hall angle. This is in contrast to the results reported for the
ferromagnetic metals Co and permalloy.",1905.00663v1
2019-05-20,Quantum drives produce strong entanglement between YIG samples without using intrinsic nonlinearities,"We show how to generate an entangled pair of yttrium iron garnet (YIG)
samples in a cavity-magnon system without using any nonlinearities which are
typically very weak. This is against the conventional wisdom which necessarily
requires strong Kerr like nonlinearity. Our key idea, which leads to
entanglement, is to drive the cavity by a weak squeezed vacuum field generated
by a flux-driven Josephson parametric amplifier (JPA). The two YIG samples
interact via the cavity. For modest values of the squeezing of the pump, we
obtain significant entanglement. This is the principal feature of our scheme.
We discuss entanglement between macroscopic spheres using several different
quantitative criteria. We show the optimal parameter regimes for obtaining
entanglement which is robust against temperature. We also discuss squeezing of
the collective magnon variables.",1905.07884v2
2019-05-28,Broadband enhancement of the magneto-optical activity of hybrid Au loaded Bi:YIG,"We unravel the underlying near-field mechanism of the enhancement of the
magneto-optical activity of bismuth-substituted yttrium iron garnet films
(Bi:YIG) loaded with gold nanoparticles. The experimental results show that the
embedded gold nanoparticles lead to a broadband enhancement of the
magneto-optical activity with respect to the activity of the bare Bi:YIG films.
Full vectorial near- and far-field simulations demonstrate that this broadband
enhancement is the result of a magneto-optically enabled cross-talking of
orthogonal localized plasmon resonances. Our results pave the way to the
on-demand design of the magneto-optical properties of hybrid magneto-plasmonic
circuitry.",1905.11941v1
2019-07-15,Tuning edge localized spin waves in magnetic microstripes by proximate magnetic structures,"The propagation of edge localized spin waves (E-SWs) in yttrium iron garnet
(YIG) microstripes with/without the proximate magnetic microstructures is
investigated by micromagnetic simulations. A splitting of the dispersion curve
with the presence of permalloy (Py) stripe is also observed. The E-SWs on the
two edges of YIG stripe have different wavelengths, group velocities, and decay
lengths at the same frequencies. The role of the Py stripe was found to be the
source of the inhomogeneous static dipolar field without dynamic coupling with
YIG. This work opens new perspectives for the design of innovative SW
interference-based logic devices.",1907.06718v1
2019-08-30,Amplitude and Phase Noise of Magnons,"The low-frequency amplitude and phase noise spectra of magnetization waves,
i.e. magnons, was measured in the yttrium iron garnet (YIG) waveguides. This
type of noise, which originates from the fluctuations of the physical
properties of the YIG crystals, has to be taken into account in the design of
YIG-based RF generators and magnonic devices for data processing, sensing and
imaging applications. It was found that the amplitude noise level of magnons
depends strongly on the power level, increasing sharply at the on-set of
nonlinear dissipation. The noise spectra of both the amplitude and phase noise
have the Lorentzian shape with the characteristic frequencies below 100 Hz.",1909.00085v1
2019-12-25,Hybrid nanophotonic-nanomagnonic SiC-YiG quantum sensor: I/ theoretical design and properties,"Here I present the theory of a new hybrid paramagnetic-ferrimagnetic SiC-YiG
quantum sensor. It is designed to allow sub-nanoscale single external spin
sensitivity optically detected pulsed electron electron double resonance
spectroscopy, using an X band pulsed EPR spectrometer and an optical fiber. The
sensor contains one single V2 negatively charged silicon vacancy color center
in 4H-SiC, whose photoluminescence is waveguided by a 4H-SiC nanophotonic
structure towards an optical fiber. This V2 spin probe is created by ion
implantation at a depth of few nanometers below the surface, determined by
optically detected paramagnetic resonance under the strong magnetic field
gradient of a YiG ferrimagnetic nanostripe located on the back-side of the
nanophotonic structure. This gradient also allow the study, slice by slice at
nanoscale, of the target paramagnetic sample. The fabrication process of this
quantum sensor, its magnetic and optical properties, its external spins sensing
properties in a structural biology context, and its integration to a standard
commercially available pulsed EPR spectrometer are all presented here.",1912.11634v1
2019-12-31,Probing magnon-magnon coupling in exchange coupled Y$_3$Fe$_5$O$_{12}$/Permalloy bilayers with magneto-optical effects,"We demonstrate the magnetically-induced transparency (MIT) effect in
Y$_3$Fe$_5$O$_{12}$(YIG)/Permalloy(Py) coupled bilayers. The measurement is
achieved via a heterodyne detection of the coupled magnetization dynamics using
a single wavelength that probes the magneto-optical Kerr and Faraday effects of
Py and YIG, respectively. Clear features of the MIT effect are evident from the
deeply modulated ferromagnetic resonance of Py due to the
perpendicular-standing-spin-wave of YIG. We develop a phenomenological model
that nicely reproduces the experimental results including the induced amplitude
and phase evolution caused by the magnon-magnon coupling. Our work offers a new
route towards studying phase-resolved spin dynamics and hybrid magnonic
systems.",1912.13407v2
2020-04-20,Ultra Thin Films of Yttrium Iron Garnet with Very Low Damping: A Review,"Thin Yttrium Iron Garnet (YIG) is a promising material for integrated
magnonics. In order to introduce YIG into nanofabrication processes it is
necessary to fabricate very thin YIG films with a thickness well below 100 nm
while retaining the extraordinary magnetic properties of the material,
especially its long magnon lifetime and spin wave propagation length. Here, we
give a brief introduction into the topic and we review and discuss the various
results published over the last decade in this area. Especially for ultrathin
films it turns out that pulsed layer deposition and sputtering are the most
promising candidates. In addition, we discuss the application of room
temperature deposition and annealing for lift-off based nanopatterning and the
properties of nanostructures obtained by this method over the past years.",2004.09094v1
2020-07-30,Coherent multi-mode conversion from microwave to optical wave via a magnon-cavity hybrid system,"Coherent conversion from microwave to optical wave opens new research avenues
towards long distant quantum network covering quantum communication, computing,
and sensing out of the laboratory. Especially multi-mode enabled system is
essential for practical applications. Here we experimentally demonstrate
coherent multi-mode conversion from the microwave to optical wave via
collective spin excitation in a single crystal yttrium iron garnet (YIG,
Y3Fe5O12) which is strongly coupled to a microwave cavity mode in a
three-dimensional rectangular cavity. Expanding collective spin excitation mode
of our magnon-cavity hybrid system from Kittel to multi magnetostatic modes, we
verify that the size of YIG sphere predominantly plays a crucial role for the
microwave-to-optical multi-mode conversion efficiency at resonant conditions.
We also find that the coupling strength between multi magnetostatic modes and a
cavity mode is manipulated by the position of a YIG inside the cavity. It is
expected to be valuable for designing a magnon hybrid system that can be used
for coherent conversion between microwave and optical photons.",2007.15299v1
2020-08-21,Integration and characterization of micron-sized YIG structures with very low Gilbert damping on arbitrary substrates,"We present a novel process that allows the transfer of monocrystalline
yttrium-iron-garnet microstructures onto virtually any kind of substrate. The
process is based on a recently developed method that allows the fabrication of
freestanding monocrystalline YIG bridges on gadolinium-gallium-garnet. Here the
bridges' spans are detached from the substrate by a dry etching process and
immersed in a watery solution. Using drop casting the immersed YIG platelets
can be transferred onto the substrate of choice, where the structures finally
can be reattached and thus be integrated into complex devices or experimental
geometries. Using time resolved scanning Kerr microscopy and inductively
measured ferromagnetic resonance we can demonstrate that the structures retain
their excellent magnetic quality. At room temperature we find a ferromagnetic
resonance linewidth of $\mu_0\Delta H_{HWHM}\approx 195\,\mu T$ and we were
even able to inductively measure magnon spectra on a single micron-sized
yttrium-iron-garnet platelet at a temperature of 5 K. The process is flexible
in terms of substrate material and shape of the structure. In the future this
approach will allow for new types of spin dynamics experiments up to now
unthinkable.",2008.09390v1
2020-11-12,"Experimental parameters, combined dynamics, and nonlinearity of a Magnonic-Opto-Electronic Oscillator (MOEO)","We report the construction and characterization of a comprehensive
magnonic-opto-electronic oscillator (MOEO) system based on 1550-nm photonics
and yttirum iron garnet (YIG) magnonics. The system exhibits a rich and
synergistic parameter space because of the ability to control individual
photonic, electronic, and magnonic components. Taking advantage of the spin
wave dispersion of YIG, the frequency self-generation as well as the related
nonlinear processes become sensitive to the external magnetic field. Besides
being known as a narrowband filter and a delay element, the YIG delayline
possesses spin wave modes that can be controlled to mix with the optoelectronic
modes to generate higher-order harmonic beating modes. With the high
sensitivity and external tunability, the MOEO system may find usefulness in
sensing applications in magnetism and spintronics beyond optoelectronics and
photonics.",2011.06155v1
2021-03-16,Spin-Phonon Interaction in Yttrium Iron Garnet,"Spin-phonon interaction is an important channel for spin and energy
relaxation in magnetic insulators. Understanding this interaction is critical
for developing magnetic insulator-based spintronic devices. Quantifying this
interaction in yttrium iron garnet (YIG), one of the most extensively
investigated magnetic insulators, remains challenging because of the large
number of atoms in a unit cell. Here, we report temperature-dependent and
polarization-resolved Raman measurements in a YIG bulk crystal. We first
classify the phonon modes based on their symmetry. We then develop a modified
mean-field theory and define a symmetry-adapted parameter to quantify
spin-phonon interaction in a phonon-mode specific way for the first time in
YIG. Based on this improved mean-field theory, we discover a positive
correlation between the spin-phonon interaction strength and the phonon
frequency.",2103.09038v1
2021-04-02,Surface plasmon-enhanced photo-magnetic excitation of spin dynamics in Au/YIG:Co magneto-plasmonic crystals,"We report strong amplification of photo-magnetic spin precession in Co-doped
YIG employing a surface plasmon excitation in a metal-dielectric
magneto-plasmonic crystal. Plasmonic enhancement is accompanied by the
localization of the excitation within the 300~nm-thick layer inside the
transparent dielectric garnet. Experimental results are nicely reproduced by
numerical simulations of the photo-magnetic excitation. Our findings
demonstrate the magneto-plasmonic concept of subwavelength localization and
amplification of the photo-magnetic excitation in dielectric YIG:Co and open up
a path to all-optical magnetization switching below diffraction limit with
energy efficiency approaching the fundamental limit for magnetic memories.",2104.01250v1
2021-05-24,Phase-resolved electrical detection of coherently coupled magnonic devices,"We demonstrate the electrical detection of magnon-magnon hybrid dynamics in
yttrium iron garnet/permalloy (YIG/Py) thin film bilayer devices. Direct
microwave current injection through the conductive Py layer excites the hybrid
dynamics consisting of the uniform mode of Py and the first standing spin wave
($n=1$) mode of YIG, which are coupled via interfacial exchange. Both the two
hybrid modes, with Py or YIG dominated excitations, can be detected via the
spin rectification signals from the conductive Py layer, providing phase
resolution of the coupled dynamics. The phase characterization is also applied
to a nonlocally excited Py device, revealing the additional phase shift due to
the perpendicular Oersted field. Our results provide a device platform for
exploring hybrid magnonic dynamics and probing their phases, which are crucial
for implementing coherent information processing with magnon excitations",2105.11057v1
2021-06-15,Nonreciprocal high-order sidebands induced by magnon Kerr nonlinearity,"We propose an effective approach for creating robust nonreciprocity of
high-order sidebands, including the first-, second- and third-order sidebands,
at microwave frequencies. This approach relies on magnon Kerr nonlinearity in a
cavity magnonics system composed of two microwave cavities and one yttrium iron
garnet (YIG) sphere. By manipulating the driving power applied on YIG and the
frequency detuning between the magnon mode in YIG and the driving field, the
effective Kerr nonlinearity can be strengthened, thereby inducing strong
transmission non-reciprocity. More interestingly, we find the higher the
sideband order, the stronger the transmission nonreciprocity marked by the
higher isolation ratio in the optimal detuning regime. Such a series of
equally-spaced high-order sidebands have potential applications in frequency
comb-like precision measurement, besides structuring high-performance on-chip
nonreciprocal devices.",2106.09542v1
2021-07-12,Origin of Perpendicular Magnetic Anisotropy in Yttrium Iron Garnet Thin Films Grown on Si (100),"We report the magnetic properties of yttrium iron garnet (YIG) thin films
grown by pulsed laser deposition technique. The films were deposited on Si
(100) substrates in the range of 15-50 nm thickness. Magnetic characterizations
were investigated by ferromagnetic resonance spectra. Perpendicular magnetic
easy axis was achieved up to 50 nm thickness. We observed that the
perpendicular anisotropy values decreased by increasing the film thickness. The
origin of the perpendicular magnetic anisotropy (PMA) was attributed to the
texture and the lattice distortion in the YIG thin films. We anticipate that
perpendicularly magnetized YIG thin films on Si substrates pave the way for a
cheaper and compatible fabrication process.",2107.05591v1
2021-10-26,Giant quadratic magneto-optical response of thin YIG films for sensitive magnetometric experiments,"We report on observation of a magneto-optical effect quadratic in
magnetization (Cotton-Mouton effect) in 50 nm thick layer of Yttrium-Iron
Garnet (YIG). By a combined theoretical and experimental approach, we managed
to quantify both linear and quadratic magneto-optical effects. We show that the
quadratic magneto-optical signal in the thin YIG film can exceed the linear
magneto-optical response, reaching values of 450 urad that are comparable with
Heusler alloys or ferromagnetic semiconductors. Furthermore, we demonstrate
that a proper choice of experimental conditions, particularly with respect to
the wavelength, is crucial for optimization of the quadratic magneto-optical
effect for magnetometry measurement.",2110.13679v1
2021-10-31,Thermally induced all-optical ferromagnetic resonance in thin YIG films,"All-optical ferromagnetic resonance (AO-FMR) is a powerful tool for local
detection of micromagnetic parameters, such as magnetic anisotropy, Gilbert
damping or spin stiffness. In this work we demonstrate that the AO-FMR method
can be used in thin films of Yttrium Iron Garnet (YIG) if a metallic capping
layer (Au, Pt) is deposited on top of the film. Magnetization precession is
triggered by heating of the metallic layer with femtosecond laser pulses. The
heating modifies the magneto-crystalline anisotropy of the YIG film and shifts
the quasi-equilibrium orientation of magnetization, which results in
precessional magnetization dynamics. The laser-induced magnetization precession
corresponds to a uniform (Kittel) magnon mode, with the precession frequency
determined by the magnetic anisotropy of the material as well as the external
magnetic field, and the damping time set by a Gilbert damping parameter. The
AO-FMR method thus enables measuring local magnetic properties, with spatial
resolution given only by the laser spot size.",2111.00586v1
2021-11-03,Efficient geometrical control of spin waves in microscopic YIG waveguides,"We study experimentally and by micromagnetic simulations the propagation of
spin waves in 100-nm thick YIG waveguides, where the width linearly decreases
from 2 to 0.5 micrometers over a transition region with varying length between
2.5 and 10 micrometers. We show that this geometry results in a down-conversion
of the wavelength, enabling efficient generation of waves with wavelengths down
to 350 nm. We also find that this geometry leads to a modification of the group
velocity, allowing for almost-dispersionless propagation of spin-wave pulses.
Moreover, we demonstrate that the influence of energy concentration outweighs
that of damping in these YIG waveguides, resulting in an overall increase of
the spin-wave intensity during propagation in the transition region. These
findings can be utilized to improve the efficiency and functionality of
magnonic devices which use spin waves as an information carrier.",2111.02236v1
2021-12-14,Robust perpendicular magnetic anisotropy in Ce substituted yttrium iron garnet epitaxial thin films,"Cerium substituted yttrium iron garnet (Ce:YIG) epitaxial thin films are
prepared on gadolinium gallium garnet (GGG) substrate with pulsed laser
deposition (PLD). It is observed that the films grown on GGG(111) substrate
exhibit perpendicular magnetic anisotropy (PMA) as compared to films grown on
GGG(100) substrate. The developed PMA is confirmed from magneto-optical Kerr
effect, bulk magnetization and ferromagnetic resonance measurements. Further,
the magnetic bubble domains are observed in the films exhibiting PMA. The
observations are explained in terms of the growth direction of Ce:YIG films and
the interplay of various magnetic anisotropy terms. The observed PMA is found
to be tunable with thickness of the film and a remarkable temperature stability
of the PMA is observed in all the studied films of Ce:YIG deposited on GGG(111)
substrate.",2112.07264v1
2022-08-08,Effect of intense x-ray free-electron laser transient gratings on the magnetic domain structure of Tm:YIG,"Magnetic patterns can be controlled globally using fields or spin polarized
currents. In contrast, the local control of the magnetization on the nanometer
length scale remains challenging. Here, we demonstrate how magnetic domain
patterns in a Tm-doped yttrium iron garnet (Tm:YIG) thin film with
perpendicular magnetic anisotropy can be permanently and locally imprinted by
high intensity photon pulses of a hard x-ray transient grating (XTG).
Micromagnetic simulations provide a qualitative understanding of the observed
changes in the orientation of magnetic domains in Tm:YIG and XTG-induced
changes. The presented results offer a route for the local manipulation of the
magnetic state using hard XTG.",2208.04200v2
2022-11-01,Design of X-Band Bicontrollable Metasurface Absorber Comprising Graphene Pixels on Copper-Backed YIG Substrate,"The planewave response of a bicontrollable metasurface absorber with
graphene-patched pixels was simulated in the X band using commercial software.
Each square meta-atom is a 4x4 array of 16 pixels, some patched with graphene
and the others unpatched. The pixels are arranged on a PVC skin which is placed
on a copper-backed YIG substrate. Graphene provides electrostatic
controllability and YIG provides magnetostatic controllability. Our design
delivers absorptance equal to or in excess of 0.9 over a 100-MHz spectral
regime in the X band, with 360 MHz/kA magnetostatic controllabity rate and 1 Hz
m/V electrostatic controllability rate. Notably, electrostatic control via
graphene in the GHz range is novel.",2211.03510v1
2022-12-03,Strong On-Chip Microwave Photon-Magnon Coupling Using Ultra-low Damping Epitaxial Y3Fe5O12 Films at 2 Kelvin,"Y3Fe5O12 is arguably the best magnetic material for magnonic quantum
information science (QIS) because of its extremely low damping. We report
ultralow damping at 2 K in epitaxial Y3Fe5O12 thin films grown on a diamagnetic
Y3Sc2Ga3O12 substrate that contains no rare-earth elements. Using these
ultralow damping YIG films, we demonstrate for the first time strong coupling
between magnons in patterned YIG thin films and microwave photons in a
superconducting Nb resonator. This result paves the road towards scalable
hybrid quantum systems that integrate superconducting microwave resonators, YIG
film magnon conduits, and superconducting qubits into on-chip QIS devices.",2212.01708v1
2023-08-01,Crystallization Dynamics of Amorphous Yttrium Iron Garnet Thin Films,"Yttrium iron garnet (YIG) is a prototypical material in spintronics due to
its exceptional magnetic properties. To exploit these properties high quality
thin films need to be manufactured. Deposition techniques like sputter
deposition or pulsed laser deposition at ambient temperature produce amorphous
films, which need a post annealing step to induce crystallization. However, not
much is known about the exact dynamics of the formation of crystalline YIG out
of the amorphous phase. Here, we conduct extensive time and temperature series
to study the crystallization behavior of YIG on various substrates and extract
the crystallization velocities as well as the activation energies needed to
promote crystallization. We find that the type of crystallization as well as
the crystallization velocity depend on the lattice mismatch to the substrate.
We compare the crystallization parameters found in literature with our results
and find an excellent agreement with our model. Our results allow us to
determine the time needed for the formation of a fully crystalline film of
arbitrary thickness for any temperature.",2308.00412v1
2023-09-12,Anisotropy-assisted magnon condensation in ferromagnetic thin films,"We theoretically demonstrate that adding an easy-axis magnetic anisotropy
facilitates magnon condensation in thin yttrium iron garnet (YIG) films.
Dipolar interactions in a quasi-equilibrium state stabilize room-temperature
magnon condensation in YIG. Even though the out-of-plane easy-axis anisotropy
generally competes with the dipolar interactions, we show that adding such
magnetic anisotropy may even assist the generation of the magnon condensate
electrically via the spin transfer torque mechanism. We use analytical
calculations and micromagnetic simulations to illustrate this effect. Our
results may explain the recent experiment on Bi-doped YIG and open a pathway
toward applying current-driven magnon condensation in quantum spintronics.",2309.05982v3
2023-11-03,Cryogenic spin Peltier effect detected by a RuO$_2$-AlO$_x$ on-chip microthermometer,"We report electric detection of the spin Peltier effect (SPE) in a bilayer
consisting of a Pt film and a Y$_{3}$Fe$_5$O$_{12}$ (YIG) single crystal at the
cryogenic temperature $T$ as low as 2 K based on a RuO$_2$$-$AlO$_x$ on-chip
thermometer film. By means of a reactive co-sputtering technique, we
successfully fabricated RuO$_2$$-$AlO$_x$ films having a large temperature
coefficient of resistance (TCR) of $\sim 100\% ~\textrm{K}^{-1}$ at around
$2~\textrm{K}$. By using the RuO$_2$$-$AlO$_x$ film as an on-chip temperature
sensor for a Pt/YIG device, we observe a SPE-induced temperature change on the
order of sub-$\mu \textrm{K}$, the sign of which is reversed with respect to
the external magnetic field $B$ direction. We found that the SPE signal
gradually decreases and converges to zero by increasing $B$ up to
$10~\textrm{T}$. The result is attributed to the suppression of magnon
excitations due to the Zeeman-gap opening in the magnon dispersion of YIG,
whose energy much exceeds the thermal energy at 2 K.",2311.01711v1
2024-03-10,Spin Waves and Spin Currents in Magnon-Phonon Composite Resonator Induced by Acoustic Waves of Various Polarizations,"In this work, we present the results of a systematic experimental study of
linear and parametric spin wave resonant excitation accompanied by spin
currents (spin pumping) in a multifrequency composite bulk acoustic wave
resonator with a ZnO-YIG-GGG-YIG/Pt structure. The features of magnetic
dynamics excitation in YIG films due to magnetoelastic coupling with acoustic
thickness modes of various polarizations are studied. Acoustic spin waves and
spin pumping are detected by simultaneous frequency-field mapping of the
inverse spin Hall effect voltage and the resonant frequencies of thickness
extensional modes. In the parametric range of frequencies and fields, acoustic
spin pumping induced by both shear and longitudinal polarization modes was
observed. Linear acoustic spin waves are excited only by shear thickness
extensional modes because longitudinal acoustic waves do not couple with the
magnetic subsystem in linear regime.",2403.06274v1
2021-04-21,Atomic Layer Deposition of Yttrium Iron Garnet Thin Films for 3D Magnetic Structures,"A wide variety of new phenomena such as novel magnetization configurations
have been predicted to occur in three dimensional magnetic nanostructures.
However, the fabrication of such structures is often challenging due to the
specific shapes required, such as magnetic tubes and spirals. Furthermore, the
materials currently used to assemble these structures are predominantly
magnetic metals that do not allow to study the magnetic response of the system
separately from the electronic one. In the field of spintronics, the
prototypical material used for such experiments is the ferrimagnetic insulator
yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$, YIG). YIG is one of the best
materials especially for magnonic studies due to its low Gilbert damping. Here,
we report the first successful fabrication of YIG thin films via atomic layer
deposition. To that end we utilize a supercycle approach based on the
combination of sub-nanometer thin layers of the binary systems Fe$_2$O$_3$ and
Y$_2$O$_3$ in the correct atomic ratio on Y$_3$Al$_5$O$_{12}$ substrates with a
subsequent annealing step. Our process is robust against typical growth-related
deviations, ensuring a good reproducibility. The ALD-YIG thin films exhibit a
good crystalline quality as well as magnetic properties comparable to other
deposition techniques. One of the outstanding characteristics of atomic layer
deposition is its ability to conformally coat arbitrarily-shaped substrates.
ALD hence is the ideal deposition technique to grant an extensive freedom in
choosing the shape of the magnetic system. The atomic layer deposition of YIG
enables the fabrication of novel three dimensional magnetic nanostructures,
which in turn can be utilized for experimentally investigating the phenomena
predicted in those structures.",2104.10293v2
2014-08-25,Measurements of the exchange stiffness of YIG films by microwave resonance techniques,"Measurements of the exchange stiffness $D$ and the exchange constant $A$ of
Yttrium Iron Garnet (YIG) films are presented. The YIG films with thicknesses
from 0.9 $\mu$m to 2.6 $\mu$m were investigated with a microwave setup in a
wide frequency range from 5 to 40 GHz. The measurements were performed when the
external static magnetic field was applied in-plane and out-of-plane. The
method of Schreiber and Frait, based on the analysis of the perpendicular
standing spin wave (PSSW) mode frequency dependence on the applied out-of-plane
magnetic field, was used to obtain the exchange stiffness $D$. This method was
modified to avoid the influence of internal magnetic fields during the
determination of the exchange stiffness. Furthermore, the method was adapted
for in-plane measurements as well. The results obtained using all methods are
compared and values of $D$ between $(5.18\pm0.01) \cdot 10^{-17}$T$\cdot$m$^2$
and $(5.34\pm0.02) \cdot 10^{-17}$ T$\cdot$m$^2$ were obtained for different
thicknesses. From this the exchange constant was calculated to be $A=(3.65 \pm
0.38)~$pJ/m.",1408.5772v1
2014-11-12,Magnonic Holographic Memory: from Proposal to Device,"In this work, we present recent developments in magnonic holographic memory
devices exploiting spin waves for information transfer. The devices comprise a
magnetic matrix and spin wave generating/detecting elements placed on the edges
of the waveguides. The matrix consists of a grid of magnetic waveguides
connected via cross junctions. Magnetic memory elements are incorporated within
the junction while the read-in and read-out is accomplished by the spin waves
propagating through the waveguides. We present experimental data on spin wave
propagation through NiFe and YIG magnetic crosses. The obtained experimental
data show prominent spin wave signal modulation (up to 20 dB for NiFe and 35 dB
for YIG) by the external magnetic field, where both the strength and the
direction of the magnetic field define the transport between the cross arms. We
also present experimental data on the 2-bit magnonic holographic memory built
on the double cross YIG structure with micro-magnets placed on the top of each
cross. It appears possible to recognize the state of each magnet via the
interference pattern produced by the spin waves with all experiments done at
room temperature. Magnonic holographic devices aim to combine the advantages of
magnetic data storage with wave-based information transfer. We present
estimates on the spin wave holographic devices performance, including power
consumption and functional throughput. According to the estimates, magnonic
holographic devices may provide data processing rates higher than 10^18
bits/cm2/s while consuming 0.15uW. Technological challenges and fundamental
physical limits of this approach are also discussed.",1411.3388v1
2015-04-10,Long range pure magnon spin diffusion observed in a non-local spin-Seebeck geometry,"The spin diffusion length for thermally excited magnon spins is measured by
utilizing a non-local spin-Seebeck effect measurement. In a bulk single crystal
of yttrium iron garnet (YIG) a focused laser thermally excites magnon spins.
The spins diffuse laterally and are sampled using a Pt inverse spin Hall effect
detector. Thermal transport modeling and temperature dependent measurements
demonstrate the absence of spurious temperature gradients beneath the Pt
detector and confirm the non-local nature of the experimental geometry.
Remarkably, we find that thermally excited magnon spins in YIG travel over 120
$\mu$m at 23 K, indicating that they are robust against inelastic scattering.
The spin diffusion length is found to be at least 47 $\mu$m and as high as 73
$\mu$m at 23 K in YIG, while at room temperature it drops to less than 10
$\mu$m. Based on this long spin diffusion length, we envision the development
of thermally powered spintronic devices based on electrically insulating, but
spin conducting materials.",1504.02808v2
2015-06-19,Origin of the thickness-dependent low-temperature enhancement of spin Seebeck effect in YIG films,"The temperature dependent longitudinal spin Seebeck effect (SSE) in heavy
metal (HM)/ Y3Fe5O12 (YIG) bilayers is investigated as a function of different
magnetic field strength, different HM detection material, and YIG thickness
ranging from nm to mm. A large enhancement of the SSE signal is observed at low
temperatures leading to a peak of the signal amplitude. We demonstrate that
this enhancement shows a clear dependence on the film thickness, being more
pronounced for thicker films and vanishing for films thinner than 600 nm. The
peak temperature depends on the applied magnetic field strength as well as on
the detection material and interface, revealing a more complex behavior beyond
the currently discussed phonon-magnon coupling mechanism that considers only
bulk effects. While the thickness dependence and magnetic field dependence can
be well explained in the framework of the magnon-driven SSE by taking into
account the frequency dependent propagation length of thermally excited magnons
in the bulk material, the temperature dependence of the SSE is significantly
influenced by the interface coupling to an adjacent detection layer. This
indicates that previously neglected interface effects play a key role and that
the spin current traversing the interface and being detected in the HM depends
differently on the magnon frequency for different HMs.",1506.06037v1
2015-08-30,Spin-transfer torque based damping control of parametrically excited spin waves in a magnetic insulator,"The damping of spin waves parametrically excited in the magnetic insulator
Yttrium Iron Garnet (YIG) is controlled by a dc current passed through an
adjacent normal-metal film. The experiment is performed on a macroscopically
sized YIG(100nm)/Pt(10nm) bilayer of 4x2 mm^2 lateral dimensions. The spin-wave
relaxation frequency is determined via the threshold of the parametric
instability measured by Brillouin light scattering (BLS) spectroscopy. The
application of a dc current to the Pt film leads to the formation of a
spin-polarized electron current normal to the film plane due to the spin Hall
effect (SHE). This spin current exerts a spin transfer torque (STT) in the YIG
film and, thus, changes the spin-wave damping. Depending on the polarity of the
applied dc current with respect to the magnetization direction, the damping can
be increased or decreased. The magnitude of its variation is proportional to
the applied current. A variation in the relaxation frequency of +/-7.5% is
achieved for an applied dc current density of 5*10^10 A/m^2.",1508.07517v1
2015-12-03,Cavity quantum electrodynamics with ferromagnetic magnons in a small yttrium-iron-garnet sphere,"Hybridizing collective spin excitations and a cavity with high cooperativity
provides a new research subject in the field of cavity quantum electrodynamics
and can also have potential applications to quantum information. Here we report
an experimental study of cavity quantum electrodynamics with ferromagnetic
magnons in a small yttrium-iron-garnet (YIG) sphere at both cryogenic and room
temperatures. We observe for the first time a strong coupling of the same
cavity mode to both a ferromagnetic-resonance (FMR) mode and a magnetostatic
(MS) mode near FMR in the quantum limit. This is achieved at a temperature ~ 22
mK, where the average microwave photon number in the cavity is less than one.
At room temperature, we also observe strong coupling of the cavity mode to the
FMR mode in the same YIG sphere and find a slight increase of the damping rate
of the FMR mode. These observations reveal the extraordinary robustness of the
FMR mode against temperature. However, the MS mode becomes unobservable at room
temperature in the measured transmission spectrum of the microwave cavity
containing the YIG sphere. Our numerical simulations show that this is due to a
drastic increase of the damping rate of the MS mode.",1512.00983v1
2017-01-25,Hybrid nanodiamond-YIG systems for efficient quantum information processing and nanoscale sensing,"The nitrogen-vacancy (NV) center in diamond has been extensively studied in
recent years for its remarkable quantum coherence properties that make it an
ideal candidate for room temperature quantum computing and quantum sensing
schemes. However, these schemes rely on spin-spin dipolar interactions, which
require the NV centers to be within a few nanometers from each other while
still separately addressable, or to be in close proximity of the diamond
surface, where their coherence properties significantly degrade. Here we
demonstrate a method for overcoming these limitations using a hybrid yttrium
iron garnet (YIG)-nanodiamond quantum system constructed with the help of
directed assembly and transfer printing techniques. We show that YIG spin-waves
can amplify the oscillating field of a microwave source by more than two orders
of magnitude and efficiently mediate its coherent interactions with an NV
center ensemble. These results demonstrate that spin-waves in ferromagnets can
be used as quantum buses for enhanced, long-range qubit interactions, paving
the way to ultra-efficient manipulation and coupling of solid state defects in
hybrid quantum networks and sensing devices.",1701.07401v1
2017-09-30,Tuning the diffusion of magnon in Y3Fe5O12 by light excitation,"Deliberate control of magnon transportation will lead to an energy-efficient
technology for information transmission and processing. Y3Fe5O12(YIG),
exhibiting extremely large magnon diffusion length due to the low magnetic
damping constant, has been intensively investigated for decades. While most of
the previous works focused on the determination of magnon diffusion length by
various techniques, herein we demonstrated how to tune magnon diffusion by
light excitation. We found that the diffusion length of thermal magnons is
strongly dependent on light wavelength when the magnon is generated by exposing
YIG directly to laser beam. The diffusion length, determined by a nonlocal
geometry at room temperature, is ~30 um for the magnons produced by visible
light (400-650 nm), and ~136-156 um for the laser between 808 nm and 980 nm.
The diffusion distance is much longer than the reported value. In addition to
thermal gradient, we found that light illumination affected the electron
configuration of the Fe3+ ion in YIG. Long wavelength laser triggers a high
spin to low spin state transition of the Fe3+ ions in FeO6 octahedron. This in
turn causes a substantial softening of the magnon thus a dramatic increase in
diffusion distance. The present work paves the way towards an efficient tuning
of magnon transport behavior which is crucially important for magnon
spintronics.",1710.00222v2
2017-12-09,Observation of spin-orbit magnetoresistance in metallic thin films on magnetic insulators,"A magnetoresistance effect induced by the Rashba spin-orbit interaction was
predicted, but not yet observed, in bilayers consisting of normal metal and
ferromagnetic insulator. Here, we present an experimental observation of this
new type of spin-orbit magnetoresistance (SOMR) effect in a bilayer structure
Cu[Pt]/Y3Fe5O12 (YIG), where the Cu/YIG interface is decorated with nanosize Pt
islands. This new MR is apparently not caused by the bulk spin-orbit
interaction because of the negligible spin-orbit interaction in Cu and the
discontinuity of the Pt islands. This SOMR disappears when the Pt islands are
absent or located away from the Cu/YIG interface, therefore we can
unambiguously ascribe it to the Rashba spin-orbit interaction at the interface
enhanced by the Pt decoration. The numerical Boltzmann simulations are
consistent with the experimental SOMR results in the angular dependence of
magnetic field and the Cu thickness dependence. Our finding demonstrates the
realization of the spin manipulation by interface engineering.",1712.03322v1
2018-01-20,Magnon Valve Effect Between Two Magnetic Insulators,"The key physics of the spin valve involves spin-polarized conduction
electrons propagating between two magnetic layers such that the device
conductance is controlled by the relative magnetization orientation of two
magnetic layers. Here, we report the effect of a magnon valve which is made of
two ferromagnetic insulators (YIG) separated by a nonmagnetic spacer layer
(Au). When a thermal gradient is applied perpendicular to the layers, the
inverse spin Hall voltage output detected by a Pt bar placed on top of the
magnon valve depends on the relative orientation of the magnetization of two
YIG layers, indicating the magnon current induced by spin Seebeck effect at one
layer affects the magnon current in the other layer separated by Au. We
interpret the magnon valve effect by the angular momentum conversion and
propagation between magnons in two YIG layers and conduction electrons in the
Au layer. The temperature dependence of magnon valve ratio shows approximately
a power law, supporting the above magnon-electron spin conversion mechanism.
This work opens a new class of valve structures beyond the conventional spin
valves.",1801.06617v2
2018-10-28,Magnetic Resonance in Defect Spins mediated by Spin Waves,"In search of two level quantum systems that implement a qubit, the
nitrogen-vacancy (NV) center in diamond has been intensively studied for years.
Despite favorable properties such as remarkable defect spin coherence times,
the addressability of NV centers raises some technical issues. The coupling of
a single NV center to an external driving field is limited to short distances,
since an efficient coupling requires the NV to be separated by only a few
microns away from the source. As a way to overcome this problem, an enhancement
of coherent coupling between NV centers and a microwave field has recently been
experimentally demonstrated using spin waves propagating in an adjacent yttrium
iron garnet (YIG) film [1]. In this paper we analyze the optically detected
magnetic resonance spectra that arise when an NV center is placed on top of a
YIG film for a geometry similar to the one in the experiment. We analytically
calculate the oscillating magnetic field of the spin wave on top of the YIG
surface to determine the coupling of spin waves to the NV center. We compare
this coupling to the case when the spin waves are absent and the NV center is
driven only with the antenna field and show that the calculated coupling
enhancement is dramatic and agrees well with the one obtained in the recent
experiment.",1810.11841v1
2018-12-02,Direct detection of induced magnetic moment and efficient spin-to-charge conversion in graphene/ferromagnetic structures,"This article shows that the spin-to-charge current conversion in single-layer
graphene (SLG) by means of the inverse Rashba-Edelstein effect (IREE) is made
possible with the integration of this remarkable 2D-material with the unique
ferrimagnetic insulator yttrium iron garnet (YIG = $Y_{3}Fe_{5}O_{12}$) as well
as with the ferromagnetic metal permalloy (Py = $Ni_{81}Sb_{19}$). By means of
X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD)
techniques, we show that the carbon atoms of the SLG acquires an induced
magnetic moment due to the proximity effect with the magnetic layer. The spin
currents are generated in the magnetic layer by spin pumping from microwave
driven ferromagnetic resonance and are detected by a dc voltage along the
graphene layer, at room temperature. The spin-to-charge current conversion,
occurring at the graphene layer, is explained by the extrinsic spin-orbit
interaction (SOI) induced by the proximity effect with the ferromagnetic layer.
The results obtained for the SLG/YIG and SLG/Py systems confirm very similar
values for the IREE parameter, which are larger than the values reported in
previous studies for SLG. We also report systematic investigations of the
electronic and magnetic properties of the SLG/YIG by means of scanning
tunneling microscopy (STM).",1812.00455v1
2019-12-22,First-principles study of magnon-phonon interactions in gadolinium iron garnet,"We obtained the spin-wave spectrum based on a first-principles method of
exchange constants, calculated the phonon spectrum by the first-principles
phonon calculation method, and extracted the broadening of the magnon spectrum,
$\Delta \omega$, induced by magnon-phonon interactions in gadolinium iron
garnet (GdIG). Using the obtained exchange constants, we reproduce the
experimental Curie temperature and the compensation temperature from spin
models using Metropolis Monte Carlo (MC) simulations. In the lower-frequency
regime, the fitted positions of the magnon-phonon dispersion crossing points
are consistent with the inelastic neutron scattering experiment. We found that
the $\Delta \omega$ and magnon wave vector $k$ have a similar relationship in
YIG. The broadening of the acoustic spin-wave branch is proportional to
$k^{2}$, while that of the YIG-like acoustic branch and the optical branch are
a constant. At a specific $k$, the magnon-phonon thermalization time of
$\tau_{mp}$ are approximately $10^{-9}$~s, $10^{-13}$~s, and $10^{-14}$~s for
acoustic branch, YIG-like acoustic branch, and optical branch, respectively.
This research provides specific and effective information for developing a
clear understanding of the spin-wave mediated spin Seebeck effect and
complements the lack of lattice dynamics calculations of GdIG.",1912.10432v1
2020-02-19,Manipulation of coupling and magnon transport in magnetic metal-insulator hybrid structures,"Ferromagnetic metals and insulators are widely used for generation, control
and detection of magnon spin signals. Most magnonic structures are based
primarily on either magnetic insulators or ferromagnetic metals, while
heterostructures integrating both of them are less explored. Here, by
introducing a Pt/yttrium iron garnet (YIG)/permalloy (Py) hybrid structure
grown on Si substrate, we studied the magnetic coupling and magnon transmission
across the interface of the two magnetic layers. We found that within this
structure, Py and YIG exhibit an antiferromagnetic coupling field as strong as
150 mT, as evidenced by both the vibrating-sample magnetometry and polarized
neutron reflectometry measurements. By controlling individual layer thicknesses
and external fields, we realize parallel and antiparallel magnetization
configurations, which are further utilized to control the magnon current
transmission. We show that a magnon spin valve with an ON/OFF ratio of ~130%
can be realized out of this multilayer structure at room temperature through
both spin pumping and spin Seebeck effect experiments. Thanks to the efficient
control of magnon current and the compatibility with Si technology, the
Pt/YIG/Py hybrid structure could potentially find applications in magnon-based
logic and memory devices.",2002.08266v1
2022-03-20,Deposition temperature dependence of thermo-spin and magneto-thermoelectric conversion in Co$_2$MnGa films on Y$_3$Fe$_5$O$_{12}$ and Gd$_3$Ga$_5$O$_{12}$,"We have characterized Co$_2$MnGa (CMG) Heusler alloy films grown on
Y$_3$Fe$_5$O$_{12}$ (YIG) and Gd$_3$Ga$_5$O$_{12}$ (GGG) substrates at
different deposition temperatures and investigated thermo-spin and
magneto-thermoelectric conversion properties by means of a lock-in thermography
technique. X-ray diffraction, magnetization, and electrical transport
measurements show that the deposition at high substrate temperatures induces
the crystallized structures of CMG while the resistivity of the CMG films on
YIG (GGG) prepared at and above 500 {\deg}C (550 {\deg}C) becomes too high to
measure the thermo-spin and magneto-thermoelectric effects due to large
roughness, highlighting the difficulty of fabricating highly ordered continuous
CMG films on garnet structures. Our lock-in thermography measurements show that
the deposition at high substrate temperatures results in an increase in the
current-induced temperature change for CMG/GGG and a decrease in that for
CMG/YIG. The former indicates the enhancement of the anomalous Ettingshausen
effect in CMG through crystallization. The latter can be explained by the
superposition of the anomalous Ettingshausen effect and the spin Peltier effect
induced by the positive (negative) charge-to-spin conversion for the amorphous
(crystallized) CMG films. These results provide a hint to construct
spin-caloritronic devices based on Heusler alloys.",2203.10566v2
2022-05-27,Magnonic Casimir Effect in Ferrimagnets,"Quantum fluctuations are the key concepts of quantum mechanics. Quantum
fluctuations of quantum fields induce a zero-point energy shift under spatial
boundary conditions. This quantum phenomenon, called the Casimir effect, has
been attracting much attention beyond the hierarchy of energy scales, ranging
from elementary particle physics to condensed matter physics together with
photonics. However, the application of the Casimir effect to spintronics has
not yet been investigated enough, particularly to ferrimagnetic thin films,
although yttrium iron garnet (YIG) is one of the best platforms for
spintronics. Here we fill this gap. Using the lattice field theory, we
investigate the Casimir effect induced by quantum fields for magnons in
insulating magnets and find that the magnonic Casimir effect can arise not only
in antiferromagnets but also in ferrimagnets including YIG thin films. Our
result suggests that YIG, the key ingredient of magnon-based spintronics, can
serve also as a promising platform for manipulating and utilizing Casimir
effects, called Casimir engineering. Microfabrication technology can control
the thickness of thin films and realize the manipulation of the magnonic
Casimir effect. Thus, we pave the way for magnonic Casimir engineering.",2205.13802v3
2022-06-30,Experimental Demonstration of a Spin-Wave Lens Designed with Machine Learning,"We present the design and experimental realization of a device that acts like
a spin-wave lens i.e., it focuses spin waves to a specified location. The
structure of the lens does not resemble any conventional lens design, it is a
nonintuitive pattern produced by a machine learning algorithm. As a spin-wave
design tool, we used our custom micromagnetic solver ""SpinTorch"" that has
built-in automatic gradient calculation and can perform backpropagation through
time for spin-wave propagation. The training itself is performed with the
saturation magnetization of a YIG film as a variable parameter, with the goal
to guide spin waves to a predefined location. We verified the operation of the
device in the widely used mumax3 micromagnetic solver, and by experimental
realization. For the experimental implementation, we developed a technique to
create effective saturation-magnetization landscapes in YIG by direct
focused-ion-beam irradiation. This allows us to rapidly transfer the nanoscale
design patterns to the YIG medium, without patterning the material by etching.
We measured the effective saturation magnetization corresponding to the FIB
dose levels in advance and used this mapping to translate the designed
scatterer to the required dose levels. Our demonstration serves as a proof of
concept for a workflow that can be used to realize more sophisticated spin-wave
devices with complex functionality, e.g., spin-wave signal processors, or
neuromorphic devices.",2207.00055v1
2022-09-01,Growth parameters of Bi0.1Y2.9Fe5O12 thin films for high frequency applications,"The growth and characterization of Bismuth (Bi) substituted YIG (Bi-YIG,
Bi0.1Y2.9Fe5O12) thin films are reported. Pulsed laser deposited (PLD) films
with thicknesses ranging from 20 to 150 nm were grown on Gadolinium Gallium
Garnet substrates. Two substrate orientations of (100) and (111) were
considered. The enhanced distribution of Bi3+ ions at dodecahedral site along
(111) is observed to lead to an increment in lattice constant from 12.379
angstrom in (100) to 12.415 angstrom in (111) oriented films. Atomic force
microscopy images showed decreasing roughness with increasing film thickness.
Compared to (100) grown films, (111) oriented films showed an increase in
ferromagnetic resonance linewidth and consequent increase in Gilbert damping.
The lowest Gilbert damping values are found to be (1.06) * 10E-4 for (100) and
(2.30) * 10E-4 for (111) oriented films with thickness of 150 nm. The observed
values of extrinsic linewidth, effective magnetization, and anisotropic field
are related to thickness of the films and substrate orientation. In addition,
the in-plane angular variation established four-fold symmetry for the (100)
deposited films unlike the case of (111) deposited films. This study prescribes
growth conditions for PLD grown single-crystalline Bi-YIG films towards desired
high frequency and magneto-optical device applications.",2209.00558v1
2022-09-05,Nonlocal detection of interlayer three-magnon coupling,"A leading nonlinear effect in magnonics is the interaction that splits a
high-frequency magnon into two low-frequency ones with conserved linear
momentum. Here, we report experimental observation of nonlocal three-magnon
scattering between spatially separated magnetic systems, viz. a CoFeB nanowire
and an yttrium iron garnet (YIG) thin film. Above a certain threshold power of
an applied microwave field, a CoFeB Kittel magnon splits into a pair of
counter-propagating YIG magnons that induce voltage signals in Pt electrodes on
each side, in excellent agreement with model calculations based on the
interlayer dipolar interaction. The excited YIG magnon pairs reside mainly in
the first excited (n=1) perpdendicular standing spin-wave mode. With increasing
power, the n=1 magnons successively scatter into nodeless (n=0) magnons through
a four-magnon process. Our results help to assess non-local scattering
processes in magnonic circuits that may enable quantum entanglement between
distant magnons for quantum information applications.",2209.01875v1
2022-12-05,Propagating spin-wave spectroscopy in nanometer-thick YIG films at millikelvin temperatures,"Performing propagating spin-wave spectroscopy of thin films at millikelvin
temperatures is the next step towards the realisation of large-scale integrated
magnonic circuits for quantum applications. Here we demonstrate spin-wave
propagation in a $100\,\mathrm{nm}$-thick yttrium-iron-garnet film at the
temperatures down to $45 \,\mathrm{mK}$, using stripline nanoantennas deposited
on YIG surface for the electrical excitation and detection. The clear
transmission characteristics over the distance of $10\,\mu \mathrm{m}$ are
measured and the subtracted spin-wave group velocity and the YIG saturation
magnetisation agree well with the theoretical values. We show that the
gadolinium-gallium-garnet substrate influences the spin-wave propagation
characteristics only for the applied magnetic fields beyond $75\,\mathrm{mT}$,
originating from a GGG magnetisation up to $47 \,\mathrm{kA/m}$ at $45
\,\mathrm{mK}$. Our results show that the developed fabrication and measurement
methodologies enable the realisation of integrated magnonic quantum
nanotechnologies at millikelvin temperatures.",2212.02257v3
2023-01-31,Complete identification of spin-wave eigenmodes excited by parametric pumping in YIG microdisks,"We present the parametric excitation of spin-wave modes in YIG micro-disks
via parallel pumping. Their spectroscopy is performed using magnetic resonance
force microscopy (MRFM), while their spatial profiles are determined by
micro-focus Brillouin light scattering (BLS). We observe that almost all the
fundamental eigenmodes of an in-plane magnetized YIG micro-disk, calculated
using a micromagnetic eigenmode solver, can be excited using the parallel
pumping scheme, as opposed to the transverse one. The comparison between the
MRFM and BLS data on one side, and the simulations on the other side, provides
the complete spectroscopic labeling of over 40 parametrically excited modes.
Our findings could be promising for spin-wave-based computation schemes, in
which the amplitudes of a large number of spin-wave modes have to be
controlled.",2301.13468v1
2023-02-01,Temperature-independent ferromagnetic resonance shift in Bi-doped YIG garnets through magnetic anisotropy tuning,"Thin garnet films are becoming central for magnon-spintronics and
spin-orbitronics devices as they show versatile magnetic properties together
with low magnetic losses. These fields would benefit from materials in which
heat does not affect the magnetization dynamics, an effect known as the
non-linear thermal frequency shift. In this study, low damping Bi substituted
Iron garnet (Bi:YIG) ultra-thin films have been grown using Pulsed Laser
Deposition. Through a fine tuning of the growth parameters, the precise control
of the perpendicular magnetic anisotropy allows to achieve a full compensation
of the dipolar magnetic anisotropy. Strikingly, once the growth conditions are
optimized, varying the growth temperature from 405 {\deg}C to 475 {\deg}C as
the only tuning parameter induces the easy-axis to go from out-of-plane to
in-plane. For films that are close to the dipolar compensation, Ferromagnetic
Resonance measurements yield an effective magnetization $\mu _{0}M_{eff} (T)$
that has almost no temperature dependence over a large temperature range (260 K
to 400 K) resulting in an anisotropy temperature exponent of 2. These findings
put Bi:YIG system among the very few materials in which the temperature
dependence of the magnetic anisotropy varies at the same rate than the
saturation magnetization. This interesting behavior is ascribed
phenomenologically to the sizable orbital moment of $Bi^{3+}$.",2302.00585v1
2015-04-07,Generation of coherent spin-wave modes in Yttrium Iron Garnet microdiscs by spin-orbit torque,"Spin-orbit effects [1-4] have the potential of radically changing the field
of spintronics by allowing transfer of spin angular momentum to a whole new
class of materials. In a seminal letter to Nature [5], Kajiwara et al. showed
that by depositing Platinum (Pt, a normal metal) on top of a 1.3 $\mu$m thick
Yttrium Iron Garnet (YIG, a magnetic insulator), one could effectively transfer
spin angular momentum through the interface between these two different
materials. The outstanding feature was the detection of auto-oscillation of the
YIG when enough dc current was passed in the Pt. This finding has created a
great excitement in the community for two reasons: first, one could control
electronically the damping of insulators, which can offer improved properties
compared to metals, and here YIG has the lowest damping known in nature;
second, the damping compensation could be achieved on very large objects, a
particularly relevant point for the field of magnonics [6,7] whose aim is to
use spin-waves as carriers of information. However, the degree of coherence of
the observed auto-oscillations has not been addressed in ref. [5]. In this
work, we emphasize the key role of quasi-degenerate spin-wave modes, which
increase the threshold current. This requires to reduce both the thickness and
lateral size in order to reach full damping compensation [8] , and we show
clear evidence of coherent spin-orbit torque induced auto-oscillation in
micron-sized YIG discs of thickness 20 nm.",1504.01512v1
2018-03-02,Long lifetime of thermally-excited magnons in bulk yttrium iron garnet,"Spin currents are generated within the bulk of magnetic materials due to heat
flow, an effect called intrinsic spin-Seebeck. This bulk bosonic spin current
consists of a diffusing thermal magnon cloud, parametrized by the magnon
chemical potential ($\mu_{m}$), with a diffusion length of several microns in
yttrium iron garnet (YIG). Transient opto-thermal measurements of the
spin-Seebeck effect (SSE) as a function of temperature reveal the time
evolution of $\mu_{m}$ due to intrinsic SSE in YIG. The interface SSE develops
at times < 2 ns while the intrinsic SSE signal continues to evolve at times >
500 $\mu$s, dominating the temperature dependence of SSE in bulk YIG.
Time-dependent SSE data are fit to a multi-temperature model of coupled
spin/heat transport using finite element method (FEM), where the magnon spin
lifetime ($\tau$) and magnon-phonon thermalization time ($\tau_{mp}$) are used
as fit parameters. From 300 K to 4 K, $\tau_{mp}$ varies from 1 to 10 ns,
whereas $\tau$ varies from 2 to 60 $\mu$s with the spin lifetime peaking at 90
K. At low temperature, a reduction in $\tau$ is observed consistent with
impurity relaxation reported in ferromagnetic resonance measurements. These
results demonstrate that the thermal magnon cloud in YIG contains extremely low
frequency magnons (~10 GHz) providing spectral insight to the microscopic
scattering processes involved in magnon spin/heat diffusion.",1803.01054v3
2018-05-07,Detection of the interfacial exchange field at a ferromagnetic insulator-nonmagnetic metal interface with pure spin currents,"At the interface between a nonmagnetic metal (NM) and a ferromagnetic
insulator (FI) spin current can interact with the magnetization, leading to a
modulation of the spin current. The interfacial exchange field at these FI-NM
interfaces can be probed by placing the interface in contact with the spin
transport channel of a lateral spin valve (LSV) device and observing additional
spin relaxation processes. We study interfacial exchange field in lateral spin
valve devices where Cu spin transport channel is in proximity with
ferromagnetic insulator EuS (EuS-LSV) and yttrium iron garnet
Y$_3$Fe$_5$O$_{12}$ (YIG-LSV). The spin signals were compared with reference
lateral spin valve devices fabricated on nonmagnetic Si/SiO$_2$ substrate with
MgO or AlO$_x$ capping. The nonlocal spin valve signal is about 4 and 6 times
lower in the EuS-LSV and YIG-LSV, respectively. The suppression in the spin
signal has been attributed to enhanced surface spin-flip probability at the
Cu-EuS (or Cu-YIG) interface due to interfacial spin-orbit field. Besides spin
signal suppression we also found widely observed low temperature peak in the
spin signal at $T \sim$30 K is shifted to higher temperature in the case of
devices in contact with EuS or YIG. Temperature dependence of spin signal for
different injector-detector distances reveal fluctuating exchange field at
these interfaces cause additional spin decoherence which limit spin relaxation
time in addition to conventional sources of spin relaxation. Our results show
that temperature dependent measurement with pure spin current can be used to
probe interfacial exchange field at the ferromagnetic insulator-nonmagnetic
metal interface.",1805.02433v2
2019-05-10,Experimental Implementations of Cavity-Magnon Systems: from Ultra Strong Coupling to Applications in Precision Measurement,"Several experimental implementations of cavity-magnon systems are presented.
First an Yttrium Iron Garnet (YIG) block is placed inside a re-entrant cavity
where the resulting hybrid mode is measured to be in the ultra strong coupling
regime. When fully hybridised the ratio between the coupling rate and uncoupled
mode frequencies is determined to be $g/\omega=0.46$. Next a thin YIG cylinder
is placed inside a loop gap cavity. The bright mode of this cavity couples to
the YIG sample and is similarly measured to be in the ultra strong coupling
regime with ratio of coupling rate to uncoupled mode frequencies as
$g/\omega=0.34$. A larger spin density medium such as lithium ferrite (LiFe) is
expected to improve couplings by a factor of 1.46 in both systems as coupling
strength is shown to be proportional to the square root of spin density and
magnetic moment. Such strongly coupled systems are potentially useful for
cavity QED, hybrid quantum systems and precision dark matter detection
experiments. The YIG disc in the loop gap cavity, is, in particular, shown to
be a strong candidate for dark matter detection. Finally, a LiFe sphere inside
a two post re-entrant cavity is considered. In past work it was shown that the
magnon mode in the sample has a turnover point in frequency. Additionally, it
was predicted that if the system was engineered such that it fully hybridised
at this turnover point the cavity-magnon polariton (CMP) transition frequency
would become insensitive to both first and second order magnetic bias field
fluctuations, a result useful for precision frequency applications. This work
implements such a system by engineering the cavity mode frequency to near this
turnover point, with suppression in sensitivity to second order bias magnetic
field fluctuations shown.",1905.04002v2
2020-08-21,"Macroscopic, layered onion shell like magnetic domain structure generated in YIG film using ultrashort, megagauss magnetic pulses","Study of the formation and evolution of large scale, ordered structures is an
enduring theme in science. The generation, evolution and control of large sized
magnetic domains are intriguing and challenging tasks, given the complex nature
of competing interactions present in any magnetic system. Here, we demonstrate
large scale non-coplanar ordering of spins, driven by picosecond, megagauss
magnetic pulses derived from a high intensity, femtosecond laser. Our studies
on a specially designed Yttrium Iron Garnet (YIG)/dielectric/metal film
sandwich target, show the creation of complex, large, concentric, elliptical
shaped magnetic domains which resemble the layered shell structure of an onion.
The largest shell has a major axis of over hundreds of micrometers, in stark
contrast to conventional sub micrometer scale polygonal, striped or bubble
shaped magnetic domains found in magnetic materials, or the large dumbbell
shaped domains produced in magnetic films irradiated with accelerator based
relativistic electron beams. Through micromagnetic simulations, we show that
the giant magnetic field pulses create ultrafast terahertz (THz) spin waves. A
snapshot of these fast propagating spin waves is stored as the layered onion
shell shaped domains in the YIG film. Typically, information transport via spin
waves in magnonic devices occurs in the gigahertz (GHz) regime, where the
devices are susceptible to thermal disturbances at room temperature. Our
intense laser light pulse - YIG sandwich target combination, paves the way for
room temperature table-top THz spin wave devices, which operate just above or
in the range of the thermal noise floor. This dissipation-less device offers
ultrafast control of spin information over distances of few hundreds of
microns.",2008.09473v1
2022-10-08,One Analytical Approach of Rashba-Edelstein Magnetoresistance in 2D Materials,"We study analytically the Rashba-Edelstein magnetoresistance (REMR) in a
structure made from an insulator ferromagnet, such as yttrium iron garnet
(YIG), and a 2D material (2DM) with direct and inverse Rashba-Edelstein
effects, such as SLG and MoS$_2$. Our results represent an efficient way of
analyzing the Rashba-Edelstein effects.",2210.03854v1
2023-08-14,Investigation of Phonon Lifetimes and Magnon-Phonon Coupling in YIG/GGG Hybrid Magnonic Systems in the Diffraction Limited Regime,"Quantum memories facilitate the storage and retrieval of quantum information
for on-chip and long-distance quantum communications. Thus, they play a
critical role in quantum information processing and have diverse applications
ranging from aerospace to medical imaging fields. Bulk acoustic wave (BAW)
phonons are one of the most attractive candidates for quantum memories because
of their long lifetime and high operating frequency. In this work, we establish
a modeling approach that can be broadly used to design hybrid magnonic
high-overtone bulk acoustic wave resonator (HBAR) structures for high-density,
long-lasting quantum memories and efficient quantum transduction devices. We
illustrate the approach by investigating a hybrid magnonic system, where BAW
phonons are excited in a gadolinium iron garnet (GGG) thick film via coupling
with magnons in a patterned yttrium iron garnet (YIG) thin film. We present
theoretical and numerical analyses of the diffraction-limited BAW phonon
lifetimes, modeshapes, and their coupling strengths to magnons in planar and
confocal YIG/GGG HBAR structures. We utilize Fourier beam propagation and
Hankel transform eigenvalue problem methods and discuss the effectiveness of
the two methods to predict the HBAR phonons. We discuss strategies to improve
the phonon lifetimes, since increased lifetimes have direct implications on the
storage times of quantum states for quantum memory applications. We find that
ultra-high, diffraction-limited, cooperativities and phonon lifetimes on the
order of ~10^5 and ~10 milliseconds, respectively, could be achieved using a
CHBAR structure with 10mum lateral YIG dimension. Additionally, the confocal
HBAR structure will offer more than 100-fold improvement of integration
density. A high integration density of on-chip memory or transduction centers
is naturally desired for high-density memory or transduction devices.",2308.06896v2
2024-02-22,Laser patterning of magnonic structure via local crystallization of Yittrium Iron Garnet,"The fabrication and integration of high-quality structures of Yttrium Iron
Garnet (YIG) is critical for magnonics.Films with excellent properties are
obtained only on single crystal Gadolinium Gallium Garnet (GGG) substrates
using high-temperature processes. The subsequent realization of magnonic
structures via lithography and etching is not straightforward as it requires a
tight control of the edge roughness, to avoid magnon scattering, and
planarization in case of multilayer devices. In this work we describe a
different approach based on local laser annealing of amorphous YIG films,
avoiding the need for subjecting the entire sample to high thermal budgets and
for physical etching. Starting from amorphous and paramagnetic YIG films grown
by pulsed laser deposition at room temperature on GGG, a 405 nm laser is used
for patterning arbitrary shaped ferrimagnetic structures by local
crystallization. In thick films (160 nm) the laser induced surface corrugation
prevents the propagation of spin-wave modes in patterned conduits. For thinner
films (80 nm) coherent propagation is observed in 1.2 micron wide conduits
displaying an attenuation length of 5 micron which is compatible with a damping
coefficient of about 5e-3. Possible routes to achieve damping coefficients
compatible with state-of-the art epitaxial YIG films are discussed.",2402.14444v1
2005-04-22,Perturbation of magnetostatic modes observed by FMRFM,"Magnetostatic modes of Yttrium Iron Garnet (YIG) films are investigated by
ferromagnetic resonance force microscopy (FMRFM). A thin film ``probe'' magnet
at the tip of a compliant cantilever introduces a local inhomogeneity in the
internal field of the YIG sample. This influences the shape of the sample's
magnetostatic modes, thereby measurably perturbing the strength of the force
coupled to the cantilever. We present a theoretical model that explains these
observations; it shows that tip-induced variation of the internal field creates
either a local ``potential barrier'' or ``potential well'' for the
magnetostatic waves. The data and model together indicate that local magnetic
imaging of ferromagnets is possible, even in the presence of long-range spin
coupling, through the induction of localized magnetostatic modes predicted to
arise from sufficiently strong tip fields.",0504598v1
2009-03-17,Microscopic spin-wave theory for yttrium-iron garnet films,"Motivated by recent experiments on thin films of the ferromagnetic insulator
yttrium-iron garnet (YIG), we have developed an efficient microscopic approach
to calculate the spin-wave spectra of these systems. We model the
experimentally relevant magnon band of YIG using an effective quantum
Heisenberg model on a cubic lattice with ferromagnetic nearest neighbor
exchange and long-range dipole-dipole interactions. After a bosonization of the
spin degrees of freedom via a Holstein-Primakoff transformation and a
truncation at quadratic order in the bosons, we obtain the spin-wave spectra
for experimentally relevant parameters without further approximation by
numerical diagonalization, using efficient Ewald summation techniques to carry
out the dipolar sums. We compare our numerical results with two different
analytic approximations and with predictions based on the phenomenological
Landau-Lifshitz equation.",0903.2847v2
2009-07-16,Reverse Doppler effect in backward spin waves scattered on acoustic waves,"We report on the observation of reverse Doppler effect in backward spin waves
reflected off of surface acoustic waves. The spin waves are excited in a
yttrium iron garnet (YIG) film. Simultaneously, acoustic waves are also
generated. The strain induced by the acoustic waves in the magnetostrictive YIG
film results in the periodic modulation of the magnetic anisotropy in the film.
Thus, in effect, a travelling Bragg grating for the spin waves is produced. The
backward spin waves reflecting off of this grating exhibit a reverse Doppler
shift: shifting down rather than up in frequency when reflecting off of an
approaching acoustic wave. Similarly, the spin waves are shifted up in
frequency when reflecting from receding acoustic waves.",0907.2902v1
2012-06-29,Platinum thickness dependence of the inverse spin-Hall voltage from spin pumping in a hybrid YIG/Pt system,"We show the first experimental observation of the platinum (Pt) thickness
dependence in a hybrid YIG/Pt system of the inverse spin-Hall effect from spin
pumping, over a large frequency range and for different rf powers. From the
measurement of the dc voltage ($\Delta\textrm{V}$) at the resonant condition
and the resistance ($R$) of the Pt layer, a strong enhancement of the ratio
$\Delta\textrm{V}/R$ has been observed, which is not in agreement with previous
studies on the NiFe/Pt system. The origin of this behaviour is still unclear
and cannot be explained by the spin transport model that we have used.",1206.7080v1
2012-08-03,Field-dependence of magnon decay in yttrium iron garnet thin films,"We discuss threshold field-dependence of the decay rate of the uniform magnon
mode in yttrium iron garnet (YIG) thin films. We demonstrate that decays must
cease to exist in YIG films of thickness less than 1 \mu m, the lengthscale
defined by the exchange length. We show that due to the symmetry of the
three-magnon coupling the decay rate is linear in \Delta H=(Hc-H) in the
vicinity of the threshold field Hc instead of the step-like \Gamma
\Theta(\Delta H) expected from the two-dimensional character of magnon
excitations in such films. For thicker films, the decay rate should exhibit
multiple steps due to thresholds for decays into a sequence of the
two-dimensional magnon bands. For yet thicker films, such thresholds merge and
crossover to the three-dimensional single-mode behavior: \Gamma |\Delta
H|^{3/2}.",1208.0831v1
2012-12-10,Heat-induced damping modification in YIG/Pt hetero-structures,"We experimentally demonstrate the manipulation of magnetization relaxation
utilizing a temperature difference across the thickness of an yttrium iron
garnet/platinum (YIG/Pt) hetero-structure: the damping is either increased or
decreased depending on the sign of the temperature gradient. This effect might
be explained by a thermally-induced spin torque on the magnetization
precession. The heat-induced variation of the damping is detected by microwave
techniques as well as by a DC voltage caused by spin pumping into the adjacent
Pt layer and the subsequent conversion into a charge current by the inverse
spin Hall effect.",1212.2073v1
2013-02-25,Phase Diagram for Magnon Condensate in Yttrium Iron Garnet Film,"Recently, magnons, which are quasiparticles describing the collective motion
of spins, were found to undergo Bose-Einstein condensation (BEC) at room
temperature in films of Yttrium Iron Garnet (YIG). Unlike other quasiparticle
BEC systems, this system has a spectrum with two degenerate minima, which makes
it possible for the system to have two condensates in momentum space. Recent
Brillouin Light scattering studies for a microwave-pumped YIG film of thickness
d=5 $\mu$m and field H=1 kOe find a low-contrast interference pattern at the
characteristic wavevector $Q$ of the magnon energy minimum. In this report, we
show that this modulation pattern can be quantitatively explained as due to
non-symmetric but coherent Bose-Einstein condensation of magnons into the two
energy minima. Our theory predicts a transition from a high-contrast symmetric
phase to a low-contrast non-symmetric phase on varying the $d$ and $H$, and a
new type of collective oscillations.",1302.6128v1
2013-02-27,Optimization of the yttrium iron garnet/platinum interface for spin pumping-based applications,"The dependence of the spin pumping efficiency and the spin mixing conductance
on the surface processing of yttrium iron garnet (YIG) before the platinum (Pt)
deposition has been investigated quantitatively. The ferromagnetic resonance
driven spin pumping injects a spin polarized current into the Pt layer, which
is transformed into an electromotive force by the inverse spin Hall effect. Our
experiments show that the spin pumping effect indeed strongly depends on the
YIG/Pt interface condition. We measure an enhancement of the inverse spin Hall
voltage and the spin mixing conductance of more than two orders of magnitude
with improved sample preparation.",1302.6697v1
2013-08-15,Detection of the microwave spin pumping using the inverse spin Hall effect,"We report electrical detection of the dynamical part of the spin pumping
current emitted during ferromagnetic resonance (FMR) using the inverse Spin
Hall Effect (ISHE). The experiment is performed on a YIG$|$Pt bilayer. The
choice of YIG, a magnetic insulator, ensures that no charge current flows
between the two layers and only pure spin current produced by the magnetization
dynamics are transferred into the adjacent strong spin-orbit Pt layer via spin
pumping. To avoid measuring the parasitic eddy currents induced at the
frequency of the microwave source, a resonance at half the frequency is induced
using parametric excitation in the parallel geometry. Triggering this nonlinear
effect allows to directly detect on a spectrum analyzer the microwave component
of the ISHE voltage. Signals as large as 30 $\mu$V are measured for precession
angles of a couple of degrees. This direct detection provides a novel efficient
means to study magnetization dynamics on a very wide frequency range with great
sensitivity.",1308.3433v2
2013-10-17,Electrical Detection of Direct and Alternating Spin Current Injected from a Ferromagnetic Insulator into a Ferromagnetic Metal,"We report room temperature electrical detection of spin injection from a
ferromagnetic insulator (YIG) into a ferromagnetic metal (Permalloy, Py).
Non-equilibrium spins with both static and precessional spin polarizations are
dynamically generated by the ferromagnetic resonance of YIG magnetization, and
electrically detected by Py as dc and ac spin currents, respectively. The dc
spin current is electrically detected via the inverse spin Hall effect of Py,
while the ac spin current is converted to a dc voltage via the spin
rectification effect of Py which is resonantly enhanced by dynamic exchange
interaction between the ac spin current and the Py magnetization. Our results
reveal a new path for developing insulator spintronics, which is distinct from
the prevalent but controversial approach of using Pt as the spin current
detector.",1310.4840v1
2013-11-06,Investigation of Magnetic Proximity Effect inTa/YIG Bilayer Hall Bar Structure,"In this work, the investigation of magnetic proximity effect was extended to
Ta which has been reported to have a negative spin Hall angle.
Magnetoresistance and Hall measurements for in-plane and out-of-plane applied
magnetic field sweeps were carried out at room temperature. The size of the MR
ratio observed (~10-5) and its magnetization direction dependence are similar
to that reported in Pt/YIG, both of which can be explained by the spin Hall
magnetoresistance theory. Additionally, a flip of magnetoresistance polarity is
observed at 4 K in the temperature dependent measurements, which can be
explained by the magnetic proximity effect induced anisotropic
magnetoresistance at low temperature. Our findings suggest that both magnetic
proximity effect and spin Hall magnetoresistance have contribution to the
recently observed unconventional magnetoresistance effect.",1311.1262v1
2013-11-25,Spin-wave excitation and propagation in microstructured waveguides of yttrium iron garnet (YIG)/Pt bilayers,"We present an experimental study of spin-wave excitation and propagation in
microstructured waveguides patterned from a 100 nm thick yttrium iron garnet
(YIG)/platinum (Pt) bilayer. The life time of the spin waves is found to be
more than an order of magnitude higher than in comparably sized metallic
structures despite the fact that the Pt capping enhances the Gilbert damping.
Utilizing microfocus Brillouin light scattering spectroscopy, we reveal the
spin-wave mode structure for different excitation frequencies. An exponential
spin-wave amplitude decay length of 31 {\mu}m is observed which is a
significant step towards low damping, insulator based micro-magnonics.",1311.6305v1
2014-05-08,Enhancement of Spin Pumping in $\mathrm{Y_3Fe_5O_{12}/Pt/Ni_{81}Fe_{19}}$ Trilayer Film,"We study spin pumping in a
$\mathrm{Y_3Fe_5O_{12}(YIG)/Pt/Ni_{81}Fe_{19}(Py)}$ trilayer film by means of
the inverse spin Hall effect (ISHE). When the ferromagnets are not excited
simultaneously by a microwave, ISHE-induced voltage is of the opposite sign at
each ferromagnetic resonance (FMR). The opposite sign is consistent with spin
pumping of bilayer films. On the other hand, the voltage is of the same sign at
each FMR when both the ferromagnets are excited simultaneously. Futhermore, the
voltage greatly increases in magnitude. The observed voltage is unconventional;
neither its sign nor magnitude can be expected from spin pumping of bilayer
films. Control experiments show that the unconventional voltage is dominantly
induced by spin pumping at the Py/Pt interface. Interaction between YIG and Py
layers is a possible origin of the unconventional voltage.",1405.1929v1
2014-09-19,Perpendicularly Biased YIG Tuners for the Fermilab Recycler 52.809 MHz Cavities,"For NOvA and future experiments requiring high intensity proton beams,
Fermilab is in the process of upgrading the existing accelerator complex for
increased proton production. One such improvement is to reduce the Main
Injector cycle time, by performing slip stacking, previously done in the Main
Injector, in the now repurposed Recycler Ring. Recycler slip stacking requires
new tuneable RF cavities, discussed separately in these proceedings. These are
quarter wave cavities resonant at 52.809 MHz with a 10 kHz tuning range. The 10
kHz range is achieved by use of a tuner which has an electrical length of
approximately one half wavelength at 52.809 MHz. The tuner is constructed from
3 1/8 inch diameter rigid coaxial line, with 5 inches of its length containing
perpendicularly biased, Al doped Yttrium Iron Garnet (YIG). The tuner design,
measurements, and high power test results are presented.",1409.5762v1
2014-11-25,Longitudinal spin Seebeck effect contribution in transverse spin Seebeck effect experiments in Pt/YIG and Pt/NFO,"We investigate the inverse spin Hall voltage of a 10nm thin Pt strip
deposited on the magnetic insulators Y3Fe5O12 (YIG) and NiFe2O4 (NFO) with a
temperature gradient in the film plane. We observe characteristics typical of
the spin Seebeck effect, although we do not observe a change of sign of the
voltage at the Pt strip when it is moved from hot to cold side, which is
believed to be the most striking feature of the transverse spin Seebeck effect.
Therefore, we relate the observed voltages to the longitudinal spin Seebeck
effect generated by a parasitic out-of-plane temperature gradient, which can be
simulated by contact tips of different material and heat conductivities and by
tip heating. This work gives new insights into the interpretation of transverse
spin Seebeck effect experiments, which are still under discussion.",1411.6790v1
2014-12-11,Magnon Hall effect and anisotropic thermal transport in NiFe and YIG ferromagnets,"The Righi-Leduc effect refers to the thermal analogue of the Hall effect, for
which the electric current is replaced by the heat current and the electric
field by the temperature gradient. In both cases, the magnetic field generates
a transverse force that deviates the carriers (electron, phonon, magnon) in the
direction perpendicular to the current. In a ferromagnet, the magnetization
plays the role of the magnetic field, and the corresponding effect is called
anomalous Hall effect. Furthermore, a second transverse contribution due to the
anisotropy, the planar Hall effect, is superimposed to the anomalous Hall
effect. We report experimental evidence of the thermal counterpart of the Hall
effects in ferromagnets, namely the magnon Hall effect (or equivalently the
anomalous Righi-Leduc effect) and the planar Righi-Leduc effect, measured on
ferromagnets that are either electrical conductor (NiFe) or insulator (YIG).
The study shows the universal character of these new thermokinetic effects,
related to the intrinsic chirality of the anisotropic ferromagnetic degrees of
freedom.",1412.3723v1
2015-02-24,High Quality Yttrium Iron Garnet Grown by Room Temperature Pulsed Laser Deposition and Subsequent Annealing,"We have investigated recrystallization of amorphous Yttrium Iron Garnet (YIG)
by annealing in oxygen atmosphere. Our findings show that well below the
melting temperature the material transforms into a fully epitaxial layer with
exceptional quality, both structural and magnetic.\\ In ferromagnetic resonance
(FMR) ultra low damping and extremely narrow linewidth can be observed. For a
56 nm thick layer a damping constant of
$\alpha$=(6.63$\pm$1.50)$\cdot$10$^{-5}$ is found and the linewidth at 9.6 GHz
is as small as 1.30$\pm$0.05 Oe which are the lowest values for PLD grown thin
films reported so far. Even for a 20 nm thick layer a damping constant of
$\alpha$=(7.51$\pm$1.40)$\cdot$10$^{-5}$ is found which is the lowest value for
ultrathin films published so far. The FMR linewidth in this case is
3.49$\pm$0.10 Oe at 9.6 GHz. Our results not only present a method of
depositing thin film YIG of unprecedented quality but also open up new options
for the fabrication of thin film complex oxides or even other crystalline
materials.",1502.06724v2
2015-05-23,Long distance transport of magnon spin information in a magnetic insulator at room temperature,"The transport of spin information has been studied in various materials, such
as metals, semiconductors and graphene. In these materials, spin is transported
by diffusion of conduction electrons. Here we study the diffusion and
relaxation of spin in a magnetic insulator, where the large bandgap prohibits
the motion of electrons. Spin can still be transported, however, through the
diffusion of non-equilibrium magnons, the quanta of spin wave excitations in
magnetically ordered materials. Here we show experimentally that these magnons
can be excited and detected fully electrically in linear response, and can
transport spin angular momentum through the magnetic insulator yttrium iron
garnet (YIG) over distances as large as 40 micrometer. We identify two
transport regimes: the diffusion limited regime for distances shorter than the
magnon relaxation length, and the relaxation limited regime for larger
distances. With a model similar to the diffusion-relaxation model for electron
spin transport in (semi)conducting materials, we extract the magnon relaxation
length lambda = 9.4 micrometer in a 200 nm thin YIG film at room temperature.",1505.06325v1
2015-05-28,Driving and detecting ferromagnetic resonance in insulators with the spin Hall effect,"We demonstrate the generation and detection of spin-torque ferromagnetic
resonance in Pt/YIG bilayers. A unique attribute of this system is that the
spin Hall effect lies at the heart of both the generation and detection
processes and no charge current is passing through the insulating magnetic
layer. When the YIG undergoes resonance, a dc voltage is detected
longitudinally along the Pt that can be described by two components. One is the
mixing of the spin Hall magnetoresistance with the microwave current. The other
results from spin pumping into the Pt being converted to a dc current through
the inverse spin Hall effect. The voltage is measured with applied magnetic
field directions that range in-plane to nearly perpendicular. We find that for
magnetic fields that are mostly out-of-plane, an imaginary component of the
spin mixing conductance is required to model our data.",1505.07791v1
2015-10-13,Optomagnonic whispering gallery microresonators,"Magnons in ferrimagnetic insulators such as yttrium iron garnet (YIG) have
recently emerged as promising candidates for coherent information processing in
microwave circuits. Here we demonstrate optical whispering gallery modes of a
YIG sphere interrogated by a silicon nitride photonic waveguide, with quality
factors approaching $10^6$ in the telecom c-band after surface treatments.
Moreover, in contrast to conventional Faraday setup, this implementation allows
input photon polarized colinearly to the magnetization to be scattered to a
sideband mode of orthogonal polarization. This Brillouin scattering process is
enhanced through triply resonant magnon, pump and signal photon modes - all of
whispering gallery nature - within an ""optomagnonic cavity"". Our results show
the potential use of magnons for mediating microwave-to-optical carrier
conversion.",1510.03545v1
2015-10-21,Magnetoresistance of heavy and light metal/ferromagnet bilayers,"We studied the magnetoresistance of normal metal (NM)/ferromagnet (FM)
bilayers in the linear and nonlinear (current-dependent) regimes and compared
it with the amplitude of the spin-orbit torques and thermally induced electric
fields. Our experiments reveal that the magnetoresistance of the heavy NM/Co
bilayers (NM = Ta, W, Pt) is phenomenologically similar to the spin Hall
magnetoresistance (SMR) of YIG/Pt, but has a much larger anisotropy, of the
order of 0.5%, which increases with the atomic number of the NM. This SMR-like
behavior is absent in light NM/Co bilayers (NM = Ti, Cu), which present the
standard AMR expected of polycrystalline FM layers. In the Ta, W, Pt/Co
bilayers we find an additional magnetoresistance, directly proportional to the
current and to the transverse component of the magnetization. This so-called
unidirectional SMR, of the order of 0.005%, is largest in W and correlates with
the amplitude of the antidamping spin-orbit torque. The unidirectional SMR is
below the accuracy of our measurements in YIG/Pt.",1510.06285v1
2015-12-14,Nonlocal Anomalous Hall Effect,"The anomalous Hall effect is deemed to be a unique transport property of
ferromagnetic metals, caused by the concerted action of spin polarization and
spin-orbit coupling. Nevertheless, recent experiments have shown that the
effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic
insulator (yttrium iron garnet (YIG)), even when precautions are taken to
ensure there is no induced magnetization in the metal. We propose a theory of
this effect based on the combined action of spin-dependent scattering from the
magnetic interface and the spin Hall effect in the bulk of the metal. At
variance with previous theories, we predict the effect to be of first order in
the spin-orbit coupling, just as the conventional anomalous Hall effect -- the
only difference being the spatial separation of the spin orbit interaction and
the magnetization. For this reason we name this effect \textit{nonlocal
anomalous Hall effect} and predict that its sign will be determined by the sign
of the spin Hall angle in the metal. The AH conductivity that we calculate from
our theory is in good agreement with the measured values in Pt/YIG structures.",1512.04146v1
2016-01-03,Detection of DC currents and resistance measurements in longitudinal spin Seebeck effect experiments on Pt/YIG and Pt/NFO,"In this work we investigated thin films of the ferrimagnetic insulators YIG
and NFO capped with thin Pt layers in terms of the longitudinal spin Seebeck
effect (LSSE). The electric response detected in the Pt layer under an
out-of-plane temperature gradient can be interpreted as a pure spin current
converted into a charge current via the inverse spin Hall effect. Typically,
the transverse voltage is the quantity investigated in LSSE measurements (in
the range of \mu V). Here, we present the directly detected DC current (in the
range of nA) as an alternative quantity. Furthermore, we investigate the
resistance of the Pt layer in the LSSE configuration. We found an influence of
the test current on the resistance. The typical shape of the LSSE curve varies
for increasing test currents.",1601.00304v1
2016-04-25,Magnon based logic in a multi-terminal YIG/Pt nanostructure,"Boolean logic is the foundation of modern digital information processing.
Recently, there has been a growing interest in phenomena based on pure spin
currents, which allow to move from charge to spin based logic gates. We study a
proof-of-principle logic device based on the ferrimagnetic insulator Yttrium
Iron Garnet (YIG), with Pt strips acting as injectors and detectors for
nonequilibrium magnons. We experimentally observe incoherent superposition of
magnons generated by different injectors. This allows to implement a fully
functional majority gate, enabling multiple logic operations (AND and OR) in
one and the same device. Clocking frequencies of the order of several GHz and
straightforward down-scaling make our device promising for applications.",1604.07262v1
2016-05-28,"Magnon Waves on Chains of YIG particles: Dispersion Relations, Faraday Rotation, and Power Transmission","We calculate the dispersion relations for magnon waves on a periodic chain of
spherical or cylindrical Yttrium Iron Garnet (YIG) particles. We use the
quasistatic approximation, appropriate when $kd \ll 1$, where $k$ is the wave
number and $d$ the interparticle spacing. In this regime, because of the
magnetic dipole-dipole interaction between the localized magnetic excitations
on neighboring particles, dispersive magnon waves can propagate along the
chain. The waves are analogous to plasmonic waves generated by electric
dipole-dipole interactions between plasmons on neighboring metallic particles.
The magnon waves can be longitudinal ($L$), transverse ($T$), or elliptically
polarized. We find that a linearly polarized magnon wave undergoes a Faraday
rotation as it propagates along the chain. The amount of Faraday rotation can
be tuned by varying the off-diagonal component of the permeability tensor. We
also discuss the possibility of wireless power transmission along the chain
using these coupled magnon waves.",1605.08931v1
2016-09-06,Chiral charge pumping in graphene deposited on a magnetic insulator,"We demonstrate that a sizable chiral charge pumping can be achieved at room
temperature in graphene/Yttrium Iron Garnet (YIG) bilayer systems. The effect,
which cannot be attributed to the ordinary spin pumping, reveals itself in the
creation of a dc electric field/voltage in graphene as a response to the
dynamic magnetic excitations (spin waves) in an adjacent out-of-plane
magnetized YIG film. We show that the induced voltage changes its sign when the
orientation of the static magnetization is reversed, clearly indicating the
broken spatial inversion symmetry in the studied system. The strength of effect
shows a non-monotonous dependence on the spin-wave frequency, in agreement with
the proposed theoretical model.",1609.01613v2
2016-10-18,Spin transport in antiferromagnetic NiO and magnetoresistance in Y$_3$Fe$_5$O$_{12}$/NiO/Pt structures,"We have studied spin transport and magnetoresistance in yttrium iron garnet
(YIG)/NiO/Pt trilayers with varied NiO thickness. To characterize the spin
transport through NiO we excite ferromagnetic resonance in YIG with a microwave
frequency magnetic field and detect the voltage associated with the inverse
spin-Hall effect (ISHE) in the Pt layer. The ISHE signal is found to decay
exponentially with the NiO thickness with a characteristic decay length of 3.9
nm. This is contrasted with the magnetoresistance in these same structures. The
symmetry of the magnetoresistive response is consistent with spin-Hall
magnetoresistance (SMR). However, in contrast to the ISHE response, as the NiO
thickness increases the SMR signal goes towards zero abruptly at a NiO
thickness of $\simeq$ 4 nm, highlighting the different length scales associated
with the spin-transport in NiO and SMR in such trilayers.",1610.05760v1
2016-10-26,Time-resolved measurements of surface spin-wave pulses at millikelvin temperatures,"In this work, we experimentally investigate the propagation of pulsed
magnetostatic surface spin-wave (magnon) signals in an yttrium iron garnet
(YIG) waveguide at millikelvin temperatures. Our measurements are performed in
a dilution refrigerator at microwave frequencies. The excellent signal-to-noise
ratio afforded by the low-temperature environment allows the propagation of the
pulses to be observed in detail. The work gives insight both into
low-temperature magnon dynamics in YIG and the potential application of systems
of propagating magnons to solid-state quantum information processing.",1610.08402v2
2016-10-29,Tailoring magnetic insulator proximity effects in graphene: First-principles calculations,"We report a systematic first-principles investigation of the influence of
different magnetic insulators on the magnetic proximity effect induced in
graphene. Four different magnetic insulators are considered: two ferromagnetic
europium chalcogenides namely EuO and EuS and two ferrimagnetic insulators
yttrium iron garnet (YIG) and cobalt ferrite (CFO). The obtained
exchange-splitting varies from tens to hundreds of meV. We also find an
electron doping induced by YIG and europium chalcogenides substrates, that
shift the Fermi level up to 0.78 eV and 1.3 eV respectively, whereas hole
doping up to 0.5 eV is generated by CFO. Furthermore, we study the variation of
the extracted exchange and tight binding parameters as a function of the EuO
and EuS thicknesses. We show that those parameters are robust to thickness
variation such that a single monolayer of magnetic insulator can induce a large
magnetic proximity effect on graphene. Those findings pave the way towards
possible engineering of graphene spin-gating by proximity effect especially in
view of recent experiments advancement.",1610.09554v1
2016-11-18,Temporal evolution of auto-oscillations in a YIG/Pt microdisc driven by pulsed spin Hall effect-induced spin-transfer torque,"The temporal evolution of pulsed Spin Hall Effect - Spin Transfer Torque
(SHE-STT) driven auto-oscillations in a Yttrium Iron Garnet (YIG) / platinum
(Pt) microdisc is studied experimentally using time-resolved Brillouin Light
Scattering (BLS) spectroscopy. It is demonstrated that the frequency of the
auto-oscillations is different in the center and at the edge of the
investigated disc that is related to the simultaneous STT excitation of a
bullet and a non-localized spin-wave mode. Furthermore, the magnetization
precession intensity is found to saturate on a time scale of 20 ns or longer,
depending on the current density. For this reason, our findings suggest that a
proper ratio between the current and the pulse duration is of crucial
importance for future STT-based devices.",1611.06054v1
2016-12-21,Pure spin current transport in gallium doped zinc oxide,"We study the flow of a pure spin current through zinc oxide by measuring the
spin Hall magnetoresistance (SMR) in thin film trilayer samples consisting of
bismuth-substituted yttrium iron garnet (Bi:YIG), gallium-doped zinc oxide
(Ga:ZnO), and platinum. We investigate the dependence of the SMR magnitude on
the thickness of the Ga:ZnO interlayer and compare to a Bi:YIG/Pt bilayer. We
find that the SMR magnitude is reduced by almost one order of magnitude upon
inserting a Ga:ZnO interlayer, and continuously decreases with increasing
interlayer thickness. Nevertheless, the SMR stays finite even for a
$12\;\mathrm{nm}$ thick Ga:ZnO interlayer. These results show that a pure spin
current indeed can propagate through a several nm-thick degenerately doped zinc
oxide layer. We also observe differences in both the temperature and the field
dependence of the SMR when comparing tri- and bilayers. Finally, we compare our
data to predictions of a model based on spin diffusion. This shows that
interface resistances play a crucial role for the SMR magnitude in these
trilayer structures.",1612.07239v1
2017-01-31,Lateral transport properties of thermally excited magnons in yttrium iron garnet films,"Spin information carried by magnons is attractive for computing technology
and the development of magnon-based computing circuits is of great interest.
However, magnon transport in insulators has been challenging, different from
the clear physical picture for spin transport in conductors. Here we
investigate the lateral transport properties of thermally excited magnons in
yttrium iron garnet (YIG), a model magnetic insulator. Polarity reversals of
detected spins in non-local geometry devices have been experimentally observed
and are strongly dependent on temperature, YIG film thickness, and
injector-detector separation distance. A competing two-channel transport model
for thermally excited magnons is proposed, which is qualitatively consistent
with the spin signal behavior. In addition to the fundamental significance for
thermal magnon transport, our work furthers the development of magnonics by
creating an easily accessible magnon source with controllable transport",1701.08932v1
2017-02-03,Quantitative investigation of the inverse Rashba-Edelstein effect in Bi/Ag and Ag/Bi on YIG,"The inverse Rashba-Edelstein effect (IREE) is a spin conversion mechanism
that recently attracts attention in spintronics and condensed matter physics.
In this letter, we report an investigation of the IREE in Bi/Ag by using
ferrimagnetic insulator yttrium iron garnet (YIG). We prepared two types of
samples with opposite directions of the Rashba field by changing a stacking
order of Bi and Ag. An electric current generated by the IREE was observed from
both stacks, and an efficiency of spin conversion -characterized by the IREE
length- was estimated by taking into account a number of contributions left out
in previous studies. This study provides a further insight into the IREE spin
conversion mechanism: important step towards achieving efficient spin-charge
conversion devices.",1702.00890v1
2017-04-28,Thermal Control of the Magnon-Photon Coupling in a Notch Filter coupled to a Yttrium-Iron-Garnet/Platinum System,"We report thermal control of mode hybridization between the ferromagnetic
resonance (FMR) and a planar resonator (notch filter) working at 4.74 GHz. The
chosen magnetic material is a ferrimagnetic insulator (Yttrium Iron Garnet:
YIG) covered by 6 nm of platinum (Pt). A current induced heating method has
been used in order to enhance the temperature of the YIG/Pt system. The device
permits us to control the transmission spectra and the magnon-photon coupling
strength at room temperature. These experimental findings reveal potentially
applicable tunable microwave filtering function.",1704.08896v3
2017-05-02,Magnetic Field-Free Giant Magnetoresistance in a Proximity- and Gate-Induced Graphene Spin Valve,"Due to its two dimensional nature, ferromagnetism and charge doping can be
induced by proximity and electric field effects in graphene. Taking advantage
of these features, we propose an electrically engineered spin valve by
combining two magnetic insulators (using EuO, EuS, or YIG) and three coating
gates. Two top gates are used to cancel the heavy electron doping's in these
magnets and one back gate is used to utilize the normal or half-metallic
ferromagnetisms. We demonstrate that, when the second top gate is tuned to
utilize the insulating or spin insulating states, huge giant magnetoresistance
(GMR) at high temperature (several times of $10^5\%$ at 68K and 100K) can be
achieved for EuO and YIG. These results imply a distinguished GMR that is
magnetism tunable, vertical configured (ferromagnetism versus insulating), and
magnetic field-free. Our work may offer a viable path to a tantalizing magnetic
field-free spintronics.",1705.00773v1
2017-05-18,The Final Chapter In The Saga Of YIG,"The magnetic insulator Yttrium Iron Garnet can be grown with exceptional
quality, has a ferrimagnetic transition temperature of nearly 600 K, and is
used in microwave and spintronic devices that can operate at room temperature.
The most accurate prior measurements of the magnon spectrum date back nearly 40
years, but cover only 3 of the lowest energy modes out of 20 distinct magnon
branches. Here we have used time-of-flight inelastic neutron scattering to
measure the full magnon spectrum throughout the Brillouin zone. We find that
the existing model of the excitation spectrum, well known from an earlier work
titled ""The Saga of YIG"", fails to describe the optical magnon modes. Using a
very general spin Hamiltonian, we show that the magnetic interactions are both
longer-ranged and more complex than was previously understood. The results
provide the basis for accurate microscopic models of the finite temperature
magnetic properties of Yttrium Iron Garnet, necessary for next-generation
electronic devices.",1705.06594v1
2017-07-20,Bistability of Cavity Magnon Polaritons,"We report the first observation of the magnon-polariton bistability in a
cavity magnonics system consisting of cavity photons strongly interacting with
the magnons in a small yttrium iron garnet (YIG) sphere. The bistable behaviors
are emerged as sharp frequency switchings of the cavity magnon-polaritons
(CMPs) and related to the transition between states with large and small number
of polaritons. In our experiment, we align, respectively, the [100] and [110]
crystallographic axes of the YIG sphere parallel to the static magnetic field
and find very different bistable behaviors (e.g., clockwise and
counter-clockwise hysteresis loops) in these two cases. The experimental
results are well fitted and explained as being due to the Kerr nonlinearity
with either positive or negative coefficient. Moreover, when the magnetic field
is tuned away from the anticrossing point of CMPs, we observe simultaneous
bistability of both magnons and cavity photons by applying a drive field on the
lower branch.",1707.06509v2
2018-03-09,Spin transport across antiferromagnets induced by the spin Seebeck effect,"For prospective spintronics devices based on the propagation of pure spin
currents, antiferromagnets are an interesting class of materials that
potentially entail a number of advantages as compared to ferromagnets. Here, we
present a detailed theoretical study of magnonic spin current transport in
ferromagnetic-antiferromagnetic multilayers by using atomistic spin dynamics
simulations. The relevant length scales of magnonic spin transport in
antiferromagnets are determined. We demonstrate the transfer of angular
momentum from a ferromagnet into an antiferromagnet due to the excitation of
only one magnon branch in the antiferromagnet. As an experimental system, we
ascertain the transport across an antiferromagnet in
YIG$|$Ir$_{20}$Mn$_{80}|$Pt heterostructures. We determine the spin transport
signals for spin currents generated in the YIG by the spin Seebeck effect and
compare to measurements of the spin Hall magnetoresistance in the
heterostructure stack. By means of temperature-dependent and
thickness-dependent measurements, we deduce conclusions on the spin transport
mechanism across IrMn and furthermore correlate it to its
paramagnetic-antiferromagnetic phase transition.",1803.03416v1
2018-03-15,Synthetic antiferromagnetic coupling between ultra-thin insulating garnets,"The use of magnetic insulators is attracting a lot of interest due to a rich
variety of spin-dependent phenomena with potential applications to spintronic
devices. Here we report ultra-thin yttrium iron garnet (YIG) / gadolinium iron
garnet (GdIG) insulating bilayers on gadolinium iron garnet (GGG). From spin
Hall magnetoresistance (SMR) and X-ray magnetic circular dichroism
measurements, we show that the YIG and GdIG magnetically couple antiparallel
even in moderate in-plane magnetic fields. The results demonstrate an
all-insulating equivalent of a synthetic antiferromagnet in a garnet-based thin
film heterostructure and could open new venues for insulators in magnetic
devices. As an example, we demonstrate a memory element with orthogonal
magnetization switching that can be read by SMR.",1803.05545v1
2018-04-12,Spin colossal magnetoresistance in an antiferromagnetic insulator,"Colossal magnetoresistance (CMR) refers to a large change in electrical
conductivity induced by a magnetic field in the vicinity of a metal-insulator
transition and has inspired extensive studies for decades\cite{Ramirez1997,
Tokura2006}. Here we demonstrate an analogous spin effect near the N\'eel
temperature $T_{\rm{N}}$=296 K of the antiferromagnetic insulator \CrO. Using a
yttrium iron garnet \YIG/\CrO/Pt trilayer, we injected a spin current from the
YIG into the \CrO layer, and collected via the inverse spin Hall effect the
signal transmitted in the heavy metal Pt. We observed a change by two orders of
magnitude in the transmitted spin current within 14 K of the N\'eel
temperature. This transition between spin conducting and nonconducting states
could be also modulated by a magnetic field in isothermal conditions. This
effect, that we term spin colossal magnetoresistance (SCMR), has the potential
to simplify the design of fundamental spintronics components, for instance
enabling the realization of spin current switches or spin-current based
memories.",1804.04516v1
2018-05-29,Efficient injection and detection of out-of-plane spins via the anomalous spin Hall effect in permalloy nanowires,"We report a novel mechanism for the electrical injection and detection of
out-of-plane spin accumulation via the anomalous spin Hall effect (ASHE), where
the direction of the spin accumulation can be controlled by manipulating the
magnetization of the ferromagnet. This mechanism is distinct from the spin Hall
effect (SHE), where the spin accumulation is created along a fixed direction
parallel to an interface. We demonstrate this unique property of the ASHE in
nanowires made of permalloy (Py), to inject and detect out-of-plane spin
accumulation in a magnetic insulator, yttrium iron garnet (YIG). We show that
the efficiency for the injection/detection of out-of-plane spins can be up to
50% of that of in-plane spins. We further report the possibility to detect spin
currents parallel to the Py/YIG interface for spins fully oriented in the
out-of-plane direction, resulting in a sign reversal of the non-local magnon
spin signal. The new mechanisms that we have demonstrated are highly relevant
for spin torque devices and applications.",1805.11575v1
2018-06-12,Resonant spin wave excitation in magnetoplasmonic bilayers by short laser pulses,"In magnetically ordered solids a static magnetic field can be generated by
virtue of the transverse magneto-optical Kerr effect (TMOKE). Moreover, the
latter was shown to be dramatically enhanced due to the optical excitation of
surface plasmons in nanostructures with relatively small optical losses. In
this paper we suggest a new method of resonant optical excitations in a
prototypical bilayer composed of noble metal (Au) with grating and a
ferromagnet thin film of yttrium iron garnet (YIG) via frequency comb. Based on
magnetization dynamics simulations we show that for the frequency comb with the
parameters, chosen in resonant with spin-wave excitations of YIG, TMOKE is
drastically enhanced, hinting towards possible technological applications in
the optical control of spintronics systems.",1806.04764v1
2018-07-02,Picosecond acoustic excitation driven ultrafast magnetization dynamics in dielectric Bi-substituted yttrium iron garnet,"Using femtosecond optical pulses, we have investigated the ultrafast
magnetization dynamics induced in a dielectric film of bismuth-substituted
yttrium iron garnet (Bi-YIG) buried below a thick Cu/Pt metallic bilayer. We
show that exciting the sample from Pt surface launches an acoustic strain pulse
propagating into the garnet film. We discovered that this strain pulse induces
a coherent magnetization precession in the Bi-YIG at the frequency of the
ferromagnetic resonance. The observed phenomena can be explain by
strain-induced changes of magnetocristalline anisotropy via the inverse
magnetostriction effect. These findings open new perspectives toward the
control of the magnetization in magnetic garnets embedded in complex
heterostructure devices.",1807.00610v1
2018-09-30,Magnon Valves Based on YIG/NiO/YIG All-Insulating Magnon Junctions,"As an alternative angular momentum carrier, magnons or spin waves can be
utilized to encode information and breed magnon-based circuits with ultralow
power consumption and non-Boolean data processing capability. In order to
construct such a circuit, it is indispensable to design some electronic
components with both long magnon decay and coherence length and effective
control over magnon transport. Here we show that an all-insulating magnon
junctions composed by a magnetic insulator (MI1)/antiferromagnetic insulator
(AFI)/magnetic insulator (MI2) sandwich (Y3Fe5O12/NiO/Y3Fe5O12) can completely
turn a thermogradient-induced magnon current on or off as the two Y3Fe5O12
layers are aligned parallel or anti-parallel. The magnon decay length in NiO is
about 3.5~4.5 nm between 100 K and 200 K for thermally activated magnons. The
insulating magnon valve (magnon junction), as a basic building block, possibly
shed light on the naissance of efficient magnon-based circuits, including
non-Boolean logic, memory, diode, transistors, magnon waveguide and switches
with sizable on-off ratios.",1810.00380v1
2018-10-17,Conventional magnon BEC in YIG film,"The conventional magnon Bose-Einstein condensation (BEC of magnons with k =
0) is a coherent state of excited magnons described by a common wave function.
It was observed first in antiferromagnetic superfluid states of 3He. Here we
report on the discovery of a very similar magnon BEC in ferrimagnetic film at
room temperature. The experiments were performed in Yttrium Iron Garnet (YIG)
films at a magnetic field oriented perpendicular to the film. The high-density
quasiequilibrium state of excited magnon was formed by methods of pulse and/or
Continuous Waves (CW) magnetic resonance. We have observed a Long Lived
Induction Decay Signals (LLIDS), well known as a signature of spin
superfluidity. We demonstrate that the BEC state may maintain permanently by
continuous replenishment of magnons with a small radiofrequency (RF) field. Our
finding opens the way for development of potential supermagnonic applications
at an ambient conditions.",1810.08051v2
2018-11-14,Tunable space-time crystal in room-temperature magnetodielectrics,"We report the experimental realization of a space-time crystal with tunable
periodicity in time and space in the magnon Bose-Einstein Condensate (BEC),
formed in a room-temperature Yttrium Iron Garnet (YIG) film by radio-frequency
space-homogeneous magnetic field. The magnon BEC is prepared to have a well
defined frequency and non-zero wavevector. We demonstrate how the crystalline
""density"" as well as the time and space textures of the resulting crystal may
be tuned by varying the experimental parameters: external static magnetic
field, temperature, thickness of the YIG film and power of the radio-frequency
field. The proposed space-time crystals provide a new dimension for exploring
dynamical phases of matter and can serve as a model nonlinear Floquet system,
that brings in touch the rich fields of classical nonlinear waves, magnonics
and periodically driven systems.",1811.05801v1
2019-03-01,Nanoscale X-Ray Imaging of Spin Dynamics in Yttrium Iron Garnet,"Time-resolved scanning transmission x-ray microscopy (TR-STXM) has been used
for the direct imaging of spin wave dynamics in thin film yttrium iron garnet
(YIG) with spatial resolution in the sub 100 nm range. Application of this
x-ray transmission technique to single crystalline garnet films was achieved by
extracting a lamella (13x5x0.185 $\mathrm{\mu m^3}$) of liquid phase epitaxy
grown YIG thin film out of a gadolinium gallium garnet substrate. Spin waves in
the sample were measured along the Damon-Eshbach and backward volume directions
of propagation at gigahertz frequencies and with wavelengths in a range between
100~nm and 10~$\mathrm{\mu}$m. The results were compared to theoretical models.
Here, the widely used approximate dispersion equation for dipole-exchange spin
waves proved to be insufficient for describing the observed Damon-Eshbach type
modes. For achieving an accurate description, we made use of the full
analytical theory taking mode-hybridization effects into account.",1903.00498v1
2019-03-05,Optimal mode matching in cavity optomagnonics,"Inelastic scattering of photons is a promising technique to manipulate
magnons but it suffers from weak intrinsic coupling. We theoretically discuss
an idea to increase optomagnonic coupling in optical whispering gallery mode
cavities, by generalizing previous analysis to include the exchange
interaction. We predict that the optomagnonic coupling constant to surface
magnons in yttrium iron garnet (YIG) spheres with radius $300\,\mathrm{\mu}$m
can be up to $40$ times larger than that to the macrospin Kittel mode. Whereas
this enhancement falls short of the requirements for magnon manipulation in
YIG, nanostructuring and/or materials with larger magneto-optical constants can
bridge this gap.",1903.01718v2
2019-03-09,Theory of the magnon Kerr effect in cavity magnonics,"We develop a theory for the magnon Kerr effect in a cavity magnonics system,
consisting of magnons in a small yttrium iron garnet (YIG) sphere strongly
coupled to cavity photons, and use it to study the bistability in this hybrid
system. To have a complete picture of the bistability phenomenon, we analyze
two different cases in driving the cavity magnonics system, i.e., directly
pumping the YIG sphere and the cavity, respectively. In both cases, the magnon
frequency shifts due to the Kerr effect exhibit a similar bistable behavior but
the corresponding critical powers are different. Moreover, we show how the
bistability of the system can be demonstrated using the transmission spectrum
of the cavity. Our results are valid in a wide parameter regime and generalize
the theory of bistability in a cavity magnonics system.",1903.03754v1
2019-03-14,Electrical control of spin mixing conductance in a Y$_3$Fe$_5$O$_{12}$/Platinum bilayer,"We report a tunable spin mixing conductance, up to $\pm 22\%$, in a
Y${}_{3}$Fe${}_{5}$O${}_{12}$/Platinum (YIG/Pt) bilayer.This control is
achieved by applying a gate voltage with an ionic gate technique, which
exhibits a gate-dependent ferromagnetic resonance line width. Furthermore, we
observed a gate-dependent spin pumping and spin Hall angle in the Pt layer,
which is also tunable up to $\pm$ 13.6\%. This work experimentally demonstrates
spin current control through spin pumping and a gate voltage in a YIG/Pt
bilayer, demonstrating the crucial role of the interfacial charge density for
the spin transport properties in magnetic insulator/heavy metal bilayers.",1903.05865v1
2019-03-29,Quantum Simulation of the Fermion-Boson Composite Quasi-Particles with a Driven Qubit-Magnon Hybrid Quantum System,"We experimentally demonstrate strong coupling between the ferromagnetic
magnons in a small yttrium-iron-garnet (YIG) sphere and the drive-field-induced
dressed states of a superconducting qubit, which gives rise to the double
dressing of the superconducting qubit. The YIG sphere and the superconducting
qubit are embedded in a microwave cavity and the effective coupling between
them is mediated by the virtual cavity photons. The theoretical results fit the
experimental observations well in a wide region of the drive-field power
resonantly applied to the superconducting qubit and reveal that the driven
qubit-magnon hybrid quantum system can be harnessed to emulate a
particle-hole-symmetric pair coupled to a bosonic mode. This hybrid quantum
system offers a novel platform for quantum simulation of the composite
quasi-particles consisting of fermions and bosons.",1903.12498v1
2019-05-04,Identification and time-resolved study of YIG spin wave modes in a MW cavity in strong coupling regime,"Recently, the hybridization of microwave-frequency cavity modes with
collective spin excitations attracted large interest for the implementation of
quantum computation protocols, which exploit the transfer of information among
these two physical systems. Here, we investigate the interaction among the
magnetization precession modes of a small YIG sphere and the MW electromagnetic
modes, resonating in a tridimensional aluminum cavity. In the strong coupling
regime, anti-crossing features were observed in correspondence of various
magnetostatic modes, which were excited in a magnetically saturated sample.
Time-resolved studies show evidence of Rabi oscillations, demonstrating
coherent exchange of energy among photons and magnons modes. To facilitate the
analysis of the standing spin-wave patterns, we propose here a new procedure,
based on the introduction of a novel functional variable. The resulting easier
identification of magnetostatic modes can be exploited to investigate, control
and compare many-levels hybrid systems in cavity- and opto-magnonics research.",1905.01522v2
2019-06-11,Proximity magnetoresistance in graphene induced by magnetic insulators,"We demonstrate the existence of Giant proximity magnetoresistance (PMR)
effect in a graphene spin valve where spin polarization is induced by a nearby
magnetic insulator. PMR calculations were performed for yttrium iron garnet
(YIG), cobalt ferrite (CFO), and two europium chalcogenides EuO and EuS. We
find a significant PMR (up to 100%) values defined as a relative change of
graphene conductance with respect to parallel and antiparallel alignment of two
proximity induced magnetic regions within graphene. Namely, for high Curie
temperature (Tc) CFO and YIG insulators which are particularly important for
applications, we obtain 22% and 77% at room temperature, respectively. For low
Tc chalcogenides, EuO and EuS, the PMR is 100% in both cases. Furthermore, the
PMR is robust with respect to system dimensions and edge type termination. Our
findings show that it is possible to induce spin polarized currents in graphene
with no direct injection through magnetic materials.",1906.04469v1
2019-06-30,Large spatial Schrodinger cat using a levitated ferrimagnetic nanoparticle,"The superposition principle is one of the main tenets of quantum mechanics.
Despite its counter-intuitiveness, it has been experimentally verified using
electrons, photons, atoms, and molecules. However, a similar experimental
demonstration using a nano or a micro particle is non-existent. Here in this
Letter, exploiting macroscopic quantum coherence and quantum tunneling, we
propose an experiment using levitated magnetic nanoparticle to demonstrate such
an effect. It is shown that the spatial separation between the delocalized
wavepackets of a $20~$nm ferrimagnetic yttrium iron garnet (YIG) nanoparticle
can be as large as $5~$$\mu$m. We argue that this large spatial separation can
be used to test different modifications such as collapse models to the standard
quantum mechanics. Furthermore, we show that the spatial superposition of a
core-shell structure, a YIG core and a non-magnetic silica shell, can be used
to probe quantum gravity.",1907.00415v4
2019-10-09,Magnetic field dependence of the nonlocal spin Seebeck effect in Pt/YIG/Pt systems at low temperatures,"We report the nonlocal spin Seebeck effect (nlSSE) in a lateral configuration
of Pt/Y$_3$Fe$_5$O$_{12}$(YIG)/Pt systems as a function of the magnetic field
$B$ (up to 10 T) at various temperatures $T$ (3 K < $T$ < 300 K). The nlSSE
voltage decreases with increasing $B$ in a linear regime with respect to the
input power (the applied charge-current squared $I^2$). The reduction of the
nlSSE becomes substantial when the Zeeman energy exceeds thermal energy at low
temperatures, which can be interpreted as freeze-out of magnons relevant for
the nlSSE. Furthermore, we found the non-linear power dependence of the nlSSE
with increasing $I$ at low temperatures ($T$ < 20 K), at which the $B$-induced
signal reduction becomes less visible. Our experimental results suggest that in
the non-linear regime high-energy magnons are over populated than those
expected from the thermal energy. We also estimate the magnon spin diffusion
length as functions of $B$ and $T$.",1910.04046v1
2019-10-31,Coherent spin pumping in a strongly coupled magnon-magnon hybrid system,"We experimentally identify coherent spin pumping in the magnon-magnon hybrid
modes of permalloy/yttrium iron garnet (Py/YIG) bilayers. Using broadband
ferromagnetic resonance, an ""avoided crossing"" is observed between the uniform
mode of Py and the spin wave mode of YIG due to the fieldlike interfacial
exchange coupling. We also identify additional linewidth suppression and
enhancement for the in-phase and out-of-phase hybrid modes, respectively,
\textcolor{black}{which can be interpreted as concerted dampinglike torque from
spin pumping}. Our analysis predicts inverse proportionality of both fieldlike
and dampinglike torques to the square root of the Py thickness, which
quantitatively agrees with experiments.",1910.14470v2
2019-12-29,Synchronized excitation of magnetization dynamics via spin waves in Bi-YIG thin film by slot line waveguide,"We have studied magnetization dynamics of a single Bi-YIG thin film by means
of the high frequency power response induced by a slot line waveguide. Multiple
absorption peaks that correspond to excitement states in magnetization dynamics
appeared without the ferromagnetic resonance (FMR) condition. The peaks were
strongly influenced by a waveguide line width and a distance between the lines.
Micromagnetics simulation reveals that each line induces a local magnetization
dynamics oscillation and generates spin waves. The spin wave that propagates
from one of the lines interferences with the other side of local magnetization
dynamics oscillation around the other line, resulting in an amplification of
the oscillation when they are in synchronization with each other. This
amplification occurs at both sides of the lines by the interference. Thus, the
possible mechanism of the excitation in the magnetization dynamics oscillation
is the synchronization of mutual magnetization dynamics oscillation via spin
waves. This technique resonantly excites the local magnetization dynamics
without the FMR condition, which is applicable as a highly coherent spin waves
source.",1912.12663v1
2019-12-30,Hybrid nanophotonic-nanomagnonic SiC-YiG quantum sensor: II/ optical fiber based ODMR and OP-PELDOR experiments on bulk HPSI 4H-SiC,"Here I present my first fiber based coupled optical and EPR experiments
associated to the development of a new SiC-YiG quantum sensor that I recently
theoretically described (arXiv:1912.11634). This quantum sensor was designed to
allow sub-nanoscale single external spin sensitivity optically detected pulsed
electron electron double resonance spectroscopy, using an X band pulsed EPR
spectrometer, an optical fiber, and a photoluminescence setup. First key
experiments before the demonstration of ODPELDOR spectroscopy are presented
here. They were performed on a bulk 4H-SiC sample containing an ensemble of
residual V2 color centers (spin S=3/2). Here I demonstrate i/ optical pumping
assisted pulsed EPR experiments, ii/ fiber based ODMR and optically detected
RABI oscillations, and iii/ optical pumping assisted PELDOR experiments, and
iv/ some spin wave resonance experiments. Those experiments confirm the
feasability of the new quantum sensing approach proposed.",1912.13111v1
2020-05-10,Stationary entanglement between light and microwave via ferromagnetic magnons,"We show how to generate stationary entanglement between light and microwave
in a hybrid opto-electro-magnonical system which mainly consists of a microwave
cavity, a yttrium iron garnet (YIG) sphere and a nanofiber. The optical modes
in nanofiber can evanescently coupled to whispering gallery modes, that are
able to interact with magnon mode via spin-orbit interaction, in YIG sphere,
while the microwave cavity photons and magnons are coupled through magnetic
dipole interaction simultaneously. Under reasonable parameter regimes, pretty
amount of entanglement can be generated, and it also shows persistence against
temperature. Our work is expected to provide a new perspective for building
more advanced and comprehensive quantum networks along with magnons for
fast-developing quantum technology and for studying the macroscopic quantum
phenomena.",2005.04581v3
2020-06-17,Magnon Polarons induced by a magnetic field gradient,"In this work, we report the theoretical possibility of generating magnon
polaron excitations through a space-varying magnetic field. The spatial
dependence of the magnetic field in the Zeeman interaction gives rise to a
magnon-phonon coupling when a magnetic field gradient is applied, and such a
coupling depends directly on the strength of the gradient. It is also predicted
that the direction of the magnetic field gradient allows control over which
phonon polarization couples to the magnons in the material. Here we develop the
calculations of the magnon-phonon coupling for an arbitrary (anti)ferromagnet,
which are later used to numerically study its consequences. These results are
compared to the ones obtained with the phenomenological magnetoelastic coupling
in YIG, where we show that the magnon polaron bandgap seen in YIG can be also
obtained with a magnetic field gradient of $\sim 0.1$T/m which can be achieved
with the current experimental techniques. Our results propose a new way of
controlling the magnetoelastic coupling in an arbitrary material and open a new
route to exploit the magnon-phonon interaction in magnonic and spintronic
devices.",2006.09839v1
2020-09-09,Effect of dipolar interactions on cavity magnon-polaritons,"The strong photon-magnon coupling between an electromagnetic cavity and two
yttrium iron garnet (YIG) spheres has been investigated in the context of a
strong mutual dipolar interaction between the spheres. A decrease in the
coupling strength between the YIG spheres and the electromagnetic cavity is
observed, along with an increase of the total magnetic losses, as the distance
between the spheres is decreased. A model of inhomogeneous broadening of the
ferromagnetic resonance linewidth, partly mitigated by the dipolar narrowing
effect, reproduces the reduction in the coupling strength observed
experimentally. These findings have important implications for the
understanding of strongly coupled photon-magnon system involving densely packed
magnetic objects, such as ferromagnetic nanowires arrays, in which the total
coupling strength with an electromagnetic cavity might become limited due to
mutual dipolar interactions.",2009.04557v1
2020-10-09,Einstein-Podolsky-Rosen entanglement and asymmetric steering between distant macroscopic mechanical and magnonic systems,"We propose a deterministic scheme for establishing hybrid
Einstein-Podolsky-Rosen (EPR) entanglement channel between a macroscopic
mechanical oscillator and a magnon mode in a distant yttrium-iron-garnet (YIG)
sphere across about ten gigahertz of frequency difference. The system consists
of a driven electromechanical cavity which is unidirectionally coupled to a
distant electromagnonical cavity inside which a YIG sphere is placed. We find
that far beyond the sideband-resolved regime in the electromechanical
subsystem, stationary phonon-magnon EPR entanglement can be achieved. This is
realized by utilizing the output field of the electromechanical cavity being an
intermediary which distributes the electromechanical entanglement to the
magnons, thus establishing a remote phonon-magnon entanglement. The EPR
entanglement is strong enough such that phonon-magnon quantum steering can be
attainable in an asymmetric manner. This long-distance macroscopic hybrid EPR
entanglement and steering enable potential applications not only in fundamental
tests of quantum mechanics at the macro scale, but also in quantum networking
and one-sided device-independent quantum cryptography based on magnonics and
electromechanics.",2010.04357v1
2020-12-14,Effect of magnon decays on parametrically pumped magnons,"We investigate the influence of magnon decays on the non-equilibrium dynamics
of parametrically excited magnons in the magnetic insulator yttrium-iron garnet
(YIG). Our investigations are motivated by a recent experiment by Noack et al.
[Phys. Status Solidi B 256, 1900121 (2019)] where an enhancement of the spin
pumping effect in YIG was observed near the magnetic field strength where
magnon decays via confluence of magnons becomes kinematically possible. To
explain the experimental findings, we have derived and solved kinetic equations
for the non-equilibrium magnon distribution. The effect of magnon decays is
taken into account microscopically via collision integrals derived from
interaction vertices involving three powers of magnon operators. Our results
agree quantitatively with the experimental data.",2012.07870v2
2021-03-12,Temperature dependence of the interface spin Seebeck effect,"We performed temperature-dependent optical pump - THz emission measurements
in Y3Fe5O12 (YIG)|Pt from 5 K to room temperature in the presence of an
externally applied magnetic field. We study the temperature dependence of the
spin Seebeck effect and observe a continuous increase as temperature is
decreased, opposite to what is observed in electrical measurements where the
spin Seebeck effect is suppressed as 0K is approached. By quantitatively
analysing the different contributions we isolate the temperature dependence of
the spin-mixing conductance and observe features that are correlated to the
bands of magnon spectrum in YIG.",2103.07307v1
2021-03-19,Remote magnon entanglement between two massive ferrimagnetic spheres via cavity optomagnonics,"Recent studies show that hybrid quantum systems based on magnonics provide a
new and promising platform for generating macroscopic quantum states involving
a large number of spins. Here we show how to entangle two magnon modes in two
massive yttrium-iron-garnet (YIG) spheres using cavity optomagnonics, where
magnons couple to high-quality optical whispering gallery modes supported by
the YIG sphere. The spheres can be as large as 1 mm in diameter and each sphere
contains more than $10^{18}$ spins. The proposal is based on the asymmetry of
the Stokes and anti-Stokes sidebands generated by the magnon-induced Brillouin
light scattering in cavity optomagnonics. This allows one to utilize the Stokes
and anti-Stokes scattering process, respectively, for generating and verifying
the entanglement. Our work indicates that cavity optomagnonics could be a
promising system for preparing macroscopic quantum states.",2103.10595v2
2021-04-22,Theory for electrical detection of the magnon Hall effect induced by dipolar interactions,"We derive the anomalous Hall contributions arising from dipolar interactions
to diffusive spin transport in magnetic insulators. Magnons, the carriers of
angular momentum in these systems, are shown to have a non-zero Berry
curvature, resulting in a measurable Hall effect. For yttrium iron garnet (YIG)
thin films we calculate both the anomalous and magnon spin conductivities. We
show that for a magnetic field perpendicular to the film the anomalous Hall
conductivity is finite. This results in a non-zero Hall signal, which can be
measured experimentally using Permalloy strips arranged like a Hall bar on top
of the YIG thin film. We show that electrical detection and injection of spin
is possible, by solving the resulting diffusion-relaxation equation for a Hall
bar. We predict the experimentally measurable Hall coefficient for a range of
temperatures and magnetic field strengths. Most strikingly, we show that there
is a sign change of the Hall coefficient associated with increasing the
thickness of the film.",2104.11304v1
2021-04-26,Cavity magnomechanical storage and retrieval of quantum states,"We show how a quantum state in a microwave cavity mode can be transferred to
and stored in a phononic mode via an intermediate magnon mode in a
magnomechanical system. For this we consider a ferrimagnetic yttrium iron
garnet (YIG) sphere inserted in a microwave cavity, where the microwave and
magnon modes are coupled via a magnetic-dipole interaction and the magnon and
phonon modes in the YIG sphere are coupled via magnetostrictive forces. By
modulating the cavity and magnon detunings and the driving of the magnon mode
in time, a Stimulated Raman Adiabatic Passage (STIRAP)-like coherent transfer
becomes possible between the cavity mode and the phonon mode. The phononic mode
can be used to store the photonic quantum state for long periods as it
possesses lower damping than the photonic and magnon modes. Thus our proposed
scheme offers a possibility of using magnomechanical systems as quantum memory
for photonic quantum information.",2104.12323v1
2021-10-09,Single-shot imaging of ultrafast all-optical magnetization dynamics with a spatio-temporal resolution,"We present a laboratory system for single-shot magneto-optical (MO) imaging
of ultrafast magnetization dynamics with high-sensitivity of MO rotation. We
create a stack of MO images repeatedly employing a single pair of a pump and
defocused probe pulses to induce and visualize MO changes in the sample. Both
laser beams are independently wavelength-tunable allowing for a flexible,
resonant adjustable two-color pump and probe scheme. To increase the MO
contrast the probe beam is spatially filtered. We performed the all-optical
switching experiment in Co-doped yttrium iron garnet films (YIG:Co) to
demonstrate the capability of the presented method. We determine the
spatial-temporal distribution of the effective field of photo-induced
anisotropy driving the all-optical switching of the magnetization in YIG:Co
film without an external magnetic field. Moreover, using this imaging method,
we tracked the process of the laser-induced magnetization precession.",2110.04506v1
2021-12-30,Giant magnon spin conductivity approaching the two-dimensional transport regime in ultrathin yttrium iron garnet films,"Conductivities are key material parameters that govern various types of
transport (electronic charge, spin, heat etc.) driven by thermodynamic forces.
Magnons, the elementary excitations of the magnetic order, flow under the
gradient of a magnon chemical potential in proportion to a magnon (spin)
conductivity $\sigma_{m}$. The magnetic insulator yttrium iron garnet (YIG) is
the material of choice for efficient magnon spin transport. Here we report an
unexpected giant $\sigma_{m}$ in record-thin YIG films with thicknesses down to
3.7 nm when the number of occupied two-dimensional (2D) subbands is reduced
from a large number to a few, which corresponds to a transition from 3D to 2D
magnon transport. We extract a 2D spin conductivity ($\approx1$ S) at room
temperature, comparable to the (electronic) spin conductivity of the
high-mobility two-dimensional electron gas in GaAs quantum wells at millikelvin
temperatures. Such high conductivities offer unique opportunities to develop
low-dissipation magnon-based spintronic devices.",2112.15165v3
2022-01-16,Coherent coupling of two remote magnonic resonators mediated by superconducting circuits,"We demonstrate microwave-mediated distant magnon-magnon coupling on a
superconducting circuit platform, incorporating chip-mounted single-crystal
Y$_3$Fe$_5$O$_{12}$ (YIG) spheres. Coherent level repulsion and dissipative
level attraction between the magnon modes of the two YIG spheres are
demonstrated. The former is mediated by cavity photons of a superconducting
resonator, and the latter is mediated by propagating photons of a coplanar
waveguide. Our results open new avenues towards exploring integrated hybrid
magnonic networks for coherent information processing on a quantum-compatible
superconducting platform.",2201.05937v1
2022-03-08,Interplay between nonlinear spectral shift and nonlinear damping of spin waves in ultrathin YIG waveguides,"We use the phase-resolved imaging to directly study the nonlinear
modification of the wavelength of spin waves propagating in 100-nm thick,
in-plane magnetized YIG waveguides. We show that, by using moderate microwave
powers, one can realize spin waves with large amplitudes corresponding to
precession angles in excess of 10 degrees and nonlinear wavelength variation of
up to 18 percent in this system. We also find that, at large precession angles,
the propagation of spin waves is strongly affected by the onset of nonlinear
damping, which results in a strong spatial dependence of the wavelength. This
effect leads to a spatially dependent controllability of the wavelength by the
microwave power. Furthermore, it leads to the saturation of nonlinear spectral
shift's effects several micrometers away from the excitation point. These
findings are important for the development of nonlinear, integrated spin-wave
signal processing devices and can be used to optimize their characteristics.",2203.04018v1
2022-03-15,Standing spin wave excitation in Bi:YIG films via temperature induced anisotropy changes and magnetoacoustic coupling,"Based on micromagnetic simulations and experimental observations of the
magnetization and lattice dynamics following the direct optical excitation of
the magnetic insulator Bi:YIG or indirect excitation via an optically opaque
Pt/Cu double layer, we disentangle the dynamical effects of magnetic anisotropy
and magnetoelastic coupling. The strain and temperature of the lattice are
quantified via modeling ultrafast x-ray diffraction data. Measurements of the
time-resolved magneto-optical Kerr effect agree well with the magnetization
dynamics simulated according to the excitation via two mechanisms: The
magneto-acoustic coupling to the experimentally verified strain dynamics and
the ultrafast temperature-induced transient change in the magnetic anisotropy.
The numerical modeling proves that for direct excitation both mechanisms drive
the fundamental mode with opposite phase. The relative ratio of standing
spin-wave amplitudes of higher order modes indicates that both mechanisms are
substantially active.",2203.07851v1
2022-06-09,Magnetically tunable zero-index metamaterials,"Zero-index metamaterials (ZIMs) feature a uniform electromagnetic mode over a
large area in arbitrary shapes, enabling many applications including
high-transmission supercouplers with arbitrary shapes, direction-independent
phase matching for nonlinear optics, and collective emission of many quantum
emitters. However, most ZIMs reported till date are passive, with no method for
the dynamic modulation of their electromagnetic properties. Here, we design and
fabricate a magnetically tunable ZIM consisting of yttrium iron garnet (YIG)
pillars sandwiched between two copper clad laminates in the microwave regime.
By harnessing the Cotton-Mouton effect of YIG, the metamaterial was
successfully toggled between gapless and bandgap states, leading to a ""phase
transition"" between a zero-index phase and a single negative phase of the
metamaterial. Using an S-shaped ZIM supercoupler, we experimentally
demonstrated a tunable supercoupling state with a low intrinsic loss of 0.95 dB
and a high extinction ratio of up to 30.63 dB at 9 GHz. Our work enables
dynamic modulation of the electromagnetic characteristics of ZIMs, enabling
various applications in tunable linear, nonlinear, quantum and nonreciprocal
electromagnetic devices.",2206.04237v1
2022-06-29,Spin-Wave Optics in YIG by Ion-Beam Irradiation,"We demonstrate direct focused ion beam (FIB) writing as an enabling
technology for realizing spin-wave-optics devices. It is shown that ion-beam
irradiation changes the characteristics of YIG films on a submicron scale in a
highly controlled way, allowing to engineer the magnonic index of refraction
adapted to desired applications. This technique does not physically remove
material, and allows rapid fabrication of high-quality architectures of
modified magnetization in magnonic media with minimal edge damage (compared to
more common techniques such as etching or milling). By experimentally showing
magnonic versions of a number of optical devices (lenses, gratings,
Fourier-domain processors) we envision this technology as the gateway to
building magnonic computing devices that rival their optical counterparts in
their complexity and computational power.",2206.14696v1
2022-09-09,A spinwave Ising machine,"We demonstrate a spin-wave-based time-multiplexed Ising Machine (SWIM),
implemented using a 5 $\mu$m thick Yttrium Iron Garnet (YIG) film and
off-the-shelf microwave components. The artificial Ising spins consist of
34--68 ns long 3.125 GHz spinwave RF pulses with their phase binarized using a
phase-sensitive microwave amplifier. Thanks to the very low spinwave group
velocity, the 7 mm long YIG waveguide can host an 8-spin MAX-CUT problem and
solve it in less than 4 $\mu$s while consuming only 7 $\mu$J. Using a real-time
oscilloscope, we follow the temporal evolution of each spin as the SWIM
minimizes its energy and find both uniform and domain-propagation-like
switching of the spin state. The SWIM has the potential for substantial further
miniaturization, scalability, speed, and reduced power consumption, and may
become a versatile platform for commercially feasible optimization problem
solvers with high performance.",2209.04291v1
2022-09-21,Interactive Entanglement in Hybrid Opto-magno-mechanics System,"We present a novel cavity opto-magno-mechanical hybrid system to generate
entanglements among multiple quantum carriers, such as magnons, mechanical
resonators, and cavity photons in both the optical and microwave domains. Two
Yttrium iron garnet (YIG) spheres are embedded in two separate microwave
cavities which are joined by a communal mechanical resonator. Because the
microwave cavities are separate, the ferromagnetic resonate frequencies of two
YIG spheres can be tuned independently, as well as the cavity frequencies. We
show that entanglement can be achieved with experimentally reachable
parameters. The entanglement is robust against environmental thermal noise,
owing to the mechanical cooling process achieved by the optical cavity. The
maximum entanglement among different carriers is achieved by optimizing the
parameters of the system. The individual tunability of the separated cavities
allows us to independently control the entanglement properties of different
subsystems and establish quantum channels with different entanglement
properties in one system. This work could provide promising applications in
quantum metrology and quantum information tasks.",2209.10120v2
2022-09-29,Strong to ultra-strong coherent coupling measurements in a YIG/cavity system at room temperature,"We present an experimental study of the strong to ultra-strong coupling
regimes at room temperature in frequency-reconfigurable 3D re-entrant cavities
coupled with a YIG slab. The observed coupling rate, defined as the ratio of
the coupling strength to the cavity frequency of interest, ranges from 12% to
59%. We show that certain considerations must be taken into account when
analyzing the polaritonic branches of a cavity spintronic device where the RF
field is highly focused in the magnetic material. Our observations are in
excellent agreement with electromagnetic finite element simulations in the
frequency domain.",2209.14643v2
2022-10-03,Chirality-induced one-way quantum steering between two waveguide-mediated ferrimagnetic microspheres,"One-way quantum steering is of importance for quantum technologies, such as
secure quantum teleportation. In this paper, we study the generation of one-way
quantum steering between two distant yttrium iron garnet (YIG) microspheres in
chiral waveguide electromagonics. We consider that the magnon mode with the
Kerr nonlinearity in each YIG sphere is chirally coupled to left- and
right-propagating guided photons in the waveguide. We find that quantum
steering between the magnon modes is absent with non-chirality but is present
merely in the form of one way (i.e., one-way steering) when the chirality
occurs. The maximal achievable steering is obviously improved as the chirality
degree increases. We further find that when the waveguide's outputs are
subjected to continuous homodyne detection, the steering can be considerably
enhanced and asymmetric steering with strong entanglement can also be achieved
by tuning the chirality. Our study shows that chirality can be explored to
effectively realize one-way quantum steering. Compared to other studies on
achieving asymmetric steering via controlling intrinsic dissipation, e.g.
cavity loss rates, our scheme merely depends on the chirality enabled via
positioning the micromagnets in the waveguide and is continuously adjustable
and experimentally more feasible.",2210.00710v1
2023-03-02,Unidirectional Microwave Transduction with Chirality Selected Short-Wavelength Magnon Excitations,"Nonreciprocal magnon propagation has recently become a highly potential
approach of developing chip-embedded microwave isolators for advanced
information processing. However, it is challenging to achieve large
nonreciprocity in miniaturized magnetic thin-film devices because of the
difficulty of distinguishing propagating surface spin waves along the opposite
directions when the film thickness is small. In this work, we experimentally
realize unidirectional microwave transduction with sub-micron-wavelength
propagating magnons in a yttrium iron garnet (YIG) thin film delay line. We
achieve a non-decaying isolation of 30 dB with a broad field-tunable band-pass
frequency range up to 14 GHz. The large isolation is due to the selection of
chiral magnetostatic surface spin waves with the Oersted field generated from
the coplanar waveguide antenna. Increasing the geometry ratio between the
antenna width and YIG thickness drastically reduces the nonreciprocity and
introduces additional magnon transmission bands. Our results pave the way for
on-chip microwave isolation and tunable delay line with short-wavelength
magnonic excitations.",2303.00936v1
2023-05-16,Tunable all-optical logic gates based on nonreciprocal topologically protected edge modes,"All-optical logic gates have been studied intensively for their potential to
enable broadband, low-loss, and high-speed communication. However, poor
tunability has remained a key challenge in this field. In this paper, we
propose a Y-shaped structure composed of Yttrium Iron Garnet (YIG) layers that
can serve as tunable all-optical logic gates, including, but not limited to,
OR, AND, and NOT gates, by applying external magnetic fields to magnetize the
YIG layers. Our findings demonstrate that these logic gates are based on
topologically protected one-way edge modes, ensuring exceptional robustness
against imperfections and nonlocal effects while maintaining extremely high
precision. Furthermore, the operating band of the logic gates is shown to be
tunable. In addition, we introduce a straightforward and practical method for
controlling and switching the logic gates between ""work"", ""skip"", and ""stop""
modes. These findings have important implications for the design of
high-performance and precise all-optical integrated circuits.",2305.09270v1
2023-06-07,Gain assisted controllable fast light generation in cavity magnomechanics,"We study the controllable output field generation from a cavity
magnomechanical resonator system that consists of two coupled microwave
resonators. The first cavity interacts with a ferromagnetic yttrium iron garnet
(YIG) sphere providing the magnon-photon coupling. Under passive cavities
configuration, the system displays high absorption, prohibiting output
transmission even though the dispersive response is anamolous. We replace the
second passive cavity with an active one to overcome high absorption, producing
an effective gain in the system. We show that the deformation of the YIG sphere
retains the anomalous dispersion. Further, tuning the exchange interaction
strength between the two resonators leads to the system's effective gain and
dispersive response. As a result, the advancement associated with the
amplification of the probe pulse can be controlled in the close vicinity of the
magnomechanical resonance. Furthermore, we find the existence of an upper bound
for the intensity amplification and the advancement of the probe pulse that
comes from the stability condition. These findings may find potential
applications for controlling light propagation in cavity magnomechanics.",2306.04390v1
2023-07-19,Zero-field spin waves in YIG nano-waveguides,"Spin-wave based transmission and processing of information is a promising
emerging nano-technology that can help overcome limitations of traditional
electronics based on the transfer of electrical charge. Among the most
important challenges for this technology is the implementation of spin-wave
devices that can operate without the need for an external bias magnetic field.
Here we experimentally demonstrate that this can be achieved using
sub-micrometer wide spin-wave waveguides fabricated from ultrathin films of
low-loss magnetic insulator - Yttrium Iron Garnet (YIG). We show that these
waveguides exhibit a highly stable single-domain static magnetic configuration
at zero field and support long-range propagation of spin waves with gigahertz
frequencies. The experimental results are supported by micromagnetic
simulations, which additionally provide information for optimization of
zero-field guiding structures. Our findings create the basis for the
development of energy-efficient zero-field spin-wave devices and circuits.",2307.09805v1
2023-08-25,Giant orbit-to-charge conversion induced via the inverse orbital Hall effect,"We investigate the orbit-to-charge conversion in YIG/Pt/nonmagnetic material
(NM) trilayer heterostructures. With the additional Ru layer on the top of
YIG/Pt stacks, the charge current signal increases nearly an order of magnitude
in both longitudinal spin Seebeck effect (SSE) and spin pumping (SP)
measurements. Through thickness dependence studies of the Ru metal layer and
theoretical model, we quantitatively clarify different contributions of the
increased SSE signal that mainly comes from the inverse orbital Hall effect
(IOHE) of Ru, and partially comes from the orbital sink effect in the Ru layer.
A similar enhancement of SSE(SP) signals is also observed when Ru is replaced
by other materials (Ta, W, and Cu), implying the universality of the IOHE in
transition metals. Our findings not only suggest a more efficient generation of
the charge current via the orbital angular moment channel but also provides
crucial insights into the interplay among charge, spin, and orbit.",2308.13144v1
2023-08-25,Macroscopic distant magnon modes entanglement via a squeezed reservoir,"The generation of robust entanglement in quantum system arrays is a crucial
aspect of the realization of efficient quantum information processing.
Recently, the field of quantum magnonics has garnered significant attention as
a promising platform for advancing in this direction. In our proposed scheme,
we utilize a one-dimensional array of coupled cavities, with each cavity
housing a single yttrium iron garnet (YIG) sphere coupled to the cavity mode
through magnetic dipole interaction. To induce entanglement between YIGs, we
employ a local squeezed reservoir, which provides the necessary nonlinearity
for entanglement generation. Our results demonstrate the successful generation
of bipartite and tripartite entanglement between distant magnon modes, all
achieved through a single quantum reservoir. Furthermore, the steady-state
entanglement between magnon modes is robust against magnon dissipation rates
and environment temperature. Our results may lead to applications of
cavity-magnon arrays in quantum information processing and quantum
communication systems.",2308.13586v3
2023-08-30,Chiral cavity-magnonic system for the unidirectional emission of a tunable squeezed microwave field,"Unidirectional photon emission is crucial for constructing quantum networks
and realizing scalable quantum information processing. In the present work an
efficient scheme is developed for the unidirectional emission of a tunable
squeezed microwave field. Our scheme is based on a chiral cavity magnonic
system, where a magnon mode in a single-crystalline yttrium iron garnet (YIG)
sphere is selectively coupled to one of the two degenerate rotating microwave
modes in a torus-shaped cavity with the same chirality. With the YIG sphere
driven by a two-color Floquet field to induce sidebands in the magnon-photon
coupling, we show that the unidirectional emission of a tunable squeezed
microwave field can be generated via the assistance of the dissipative magnon
mode and a waveguide. Moreover, the direction of the proposed one-way emitter
can be controlled on demand by reversing the biased magnetic field. Our work
opens up an avenue to create and manipulate one-way nonclassical microwave
radiation field and could find potential quantum technological applications.",2308.15826v1
2023-10-29,Magnomechanically controlled Goos-Hänchen shift in cavity QED,"Phenomena involving interactions among magnons, phonons, and photons in
cavity magnomechanical systems have attracted considerable attention recently,
owing to their potential applications in the microwave frequency range. One
such important effect is the response of a probe field to such tripartite
interaction between photon-magnon-phonon. In this paper, we study
Goos-H\""{a}nchen shift (GHS) of a reflected probe field in a cavity
magnomechanical system. We consider a YIG sphere positioned within a microwave
cavity. A microwave control field directly drives the magnon mode in YIG
sphere, whereas the cavity is driven via a weak probe field. Our results show
that the GHS can be coherently controlled through magnon-phonon coupling via
the control field. For instance, GHS can be tuned from positive to negative by
tuning the magnon-phonon coupling. Similarly, the effective cavity detuning is
another important controlling parameter for GHS. Furthermore, we observe that
the enhancement of GHS occurs when magnon-phonon coupling is weak at resonance,
and when the magnon-photon coupling is approximately equal to the loss of
microwave photons. Our findings may have potential significance in applications
related to microwave switching and sensing.",2310.19111v1
2023-11-13,Microwave-to-Optical Quantum Transduction Utilizing the Topological Faraday Effect of Topological Insulator Heterostructures,"The quantum transduction between microwave and optical photons is essential
for realizing scalable quantum computers with superconducting qubits. Due to
the large frequency difference between microwave and optical ranges, the
transduction needs to be done via intermediate bosonic modes or nonlinear
processes. So far, the transduction efficiency $\eta$ via the magneto-optic
Faraday effect (i.e., the light-magnon interaction) in the ferromagnet YIG has
been demonstrated to be small as $\eta\sim 10^{-8} \mathrm{-} 10^{-15}$ due to
the sample size limitation inside the cavity. Here, we take advantage of the
fact that three-dimensional topological insulator thin films exhibit a
topological Faraday effect that is independent of the sample thickness. This
leads to a large Faraday rotation angle and therefore enhanced light-magnon
interaction in the thin film limit. We show theoretically that the transduction
efficiency can be greatly improved to $\eta\sim10^{-4}$ by utilizing the
heterostructures consisting of topological insulator thin films such as
Bi$_2$Se$_3$ and ferromagnetic insulator thin films such as YIG.",2311.07293v1
2023-11-15,Broad-Wavevector Spin Pumping of Flat-Band Magnons,"We report the experimental observation of large spin pumping signals in
YIG/Pt system driven by broad-wavevector spin-wave spin current. 280 nm-wide
microwave inductive antennas offer broad-wavevector excitation which, in
combination with quasi-flatband of YIG, allows a large number of magnons to
participate in spin pumping at a given frequency. Through comparison with
ferromagnetic resonance spin pumping, we attribute the enhancement of the spin
current to the multichromatic magnons. The high efficiency of spin current
generation enables us to uncover nontrivial propagating properties in ultra-low
power regions. Additionally, our study achieves the spatially separated
detection of magnons, allowing the direct extraction of the decay length. The
synergistic combination of the capability of broad-wavevector excitation,
enhanced voltage signals, and nonlocal detection provides a new avenue for the
electrical exploration of spin waves dynamics.",2311.09098v1
2023-11-25,Spin pumping in YIG-Pt structures: the role of the van Hove singularities,"Spin pumping by surface and backward volume magnetostatic waves in YIG/Pt
structures is experimentally studied and analyzed. It is shown that at
frequencies corresponding to van Hove singularities in the density of states of
the spin wave spectrum, an increase in the efficiency of electron-magnon
scattering and spin current generation takes place. The obtained results are
important for spin wave-based spintronic devices development.",2311.15096v1
2024-02-05,Controlling magnon-photon coupling in a planar geometry,"The tunability of magnons enables their interaction with various other
quantum excitations, including photons, paving the route for novel hybrid
quantum systems. Here, we study magnon-photon coupling using a high-quality
factor split-ring resonator and single-crystal yttrium iron garnet (YIG)
spheres at room temperature. We investigate the dependence of the coupling
strength on the size of the sphere and find that the coupling is stronger for
spheres with a larger diameter as predicted by theory. Furthermore, we
demonstrate strong magnon-photon coupling by varying the position of the YIG
sphere within the resonator. Our experimental results reveal the expected
correlation between the coupling strength and the rf magnetic field. These
findings demonstrate the control of coherent magnon-photon coupling through the
theoretically predicted square-root dependence on the spin density in the
ferromagnetic medium and the magnetic dipolar interaction in a planar
resonator.",2402.03071v1
2024-03-12,Negative orbital Hall effect in Germanium,"Our investigation reveals a groundbreaking discovery of a negative inverse
orbital Hall effect (IOHE) in Ge thin films. We employed the innovative orbital
pumping technique where spin-orbital coupled current is injected into Ge films
using YIG/Pt(2)/Ge($t_{Ge}$) and YIG/W(2)/Ge($t_{Ge}$) heterostructures.
Through comprehensive analysis, we observe significant reductions in the
signals generated by coherent (RF-driven) and incoherent (thermal-driven)
spin-orbital pumping techniques. These reductions are attributed to the
presence of a remarkable strong negative IOHE in Ge, showing its magnitude
comparable to the spin-to-charge signal in Pt. Our findings reveal that
although the spin-to-charge conversion in Ge is negligible, the
orbital-to-charge conversion exhibits large magnitude. Our results are
innovative and pioneering in the investigation of negative IOHE by the
injection of spin-orbital currents.",2403.07254v1
2017-09-21,Electrical properties of single crystal Yttrium Iron Garnet ultra-thin films at high temperatures,"We report a study on the electrical properties of 19 nm thick Yttrium Iron
Garnet (YIG) films grown by liquid phase epitaxy. The electrical conductivity
and Hall coefficient are measured in the high temperature range [300,400]~K
using a Van der Pauw four-point probe technique. We find that the electrical
resistivity decreases exponentially with increasing temperature following an
activated behavior corresponding to a band-gap of $E_g\approx 2$ eV, indicating
that epitaxial YIG ultra-thin films behave as large gap semiconductor, and not
as electrical insulator. The resistivity drops to about $5\times 10^3$~$\Omega
\cdot \text{cm}$ at $T=400$ K. We also infer the Hall mobility, which is found
to be positive ($p$-type) at 5 cm$^2$/(V$\cdot$sec) and about independent of
temperature. We discuss the consequence for non-local transport experiments
performed on YIG at room temperature. These electrical properties are
responsible for an offset voltage (independent of the in-plane field direction)
whose amplitude, odd in current, grows exponentially with current due to Joule
heating. These electrical properties also induce a sensitivity to the
perpendicular component of the magnetic field through the Hall effect. In our
lateral device, a thermoelectric offset voltage is produced by a temperature
gradient along the wire direction proportional to the perpendicular component
of the magnetic field (Righi-Leduc effects).",1709.07207v1
2019-03-19,Magnetic properties and domain structure of ultrathin yttrium iron garnet/Pt bilayers,"We report on the structure, magnetization, magnetic anisotropy, and domain
morphology of ultrathin yttrium iron garnet (YIG)/Pt films with thickness
ranging from 3 to 90 nm. We find that the saturation magnetization is close to
the bulk value in the thickest films and decreases towards low thickness with a
strong reduction below 10 nm. We characterize the magnetic anisotropy by
measuring the transverse spin Hall magnetoresistance as a function of applied
field. Our results reveal strong easy plane anisotropy fields of the order of
50-100 mT, which add to the demagnetizing field, as well as weaker in-plane
uniaxial anisotropy ranging from 10 to 100 $\mu$T. The in-plane easy axis
direction changes with thickness, but presents also significant fluctuations
among samples with the same thickness grown on the same substrate. X-ray
photoelectron emission microscopy reveals the formation of zigzag magnetic
domains in YIG films thicker than 10 nm, which have dimensions larger than
several 100 $\mu$m and are separated by achiral N\'{e}el-type domain walls.
Smaller domains characterized by interspersed elongated features are found in
YIG films thinner than 10 nm.",1903.08285v1
2020-05-28,A First Principle Study on Magneto-Optical Effects and Magnetism in Ferromagnetic Semiconductors Y$_3$Fe$_5$O$_{12}$ and Bi$_3$Fe$_5$O$_{12}$,"The magneto-optical (MO) effects not only are a powerful probe of magnetism
and electronic structure of magnetic solids but also have valuable applications
in high-density data-storage technology. Yttrium iron garnet
(Y$_3$Fe$_5$O$_{12}$) (YIG) and bismuth iron garnet (Bi$_3$Fe$_5$O$_{12}$)
(BIG) are two widely used magnetic semiconductors with strong magneto-optical
effects and have also attracted the attention for fundamental physics studies.
In particular, YIG has been routinely used as a spin current injector. In this
paper, we present a thorough theoretical investigation on magnetism,
electronic, optical and MO properties of YIG and BIG, based on the density
functional theory with the generalized gradient approximation plus onsite
Coulomb repulsion. We find that both semiconductors exhibit large MO effects
with their Kerr and Faraday rotation angles being comparable to that of
best-known MO materials such as MnBi. Especially, the MO Kerr rotation angle
for bulk BIG reaches -1.2$ ^{\circ}$ at photon energy $\sim2.4$ eV, and the MO
Faraday rotation angle for BIG film reaches -74.6 $ ^{\circ}/\mu m$ at photon
energy $\sim2.7$ eV. Furthermore, we also find that both valence and conduction
bands across the MO band gap in BIG are purely spin-down states, i.e., BIG is a
single spin semiconductor. These interesting findings suggest that the iron
garnets will find valuable applications in semiconductor MO and spintronic
nanodevices. The calculated optical conductivity spectra, MO Kerr and Faraday
rotation angles agree well with the available experimental data. The main
features in the optical and MO spectra of both systems are analyzed in terms of
the calculated band structures especially by determining the band state
symmetries and the main optical transitions at the $\Gamma$ point in the
Brillouin zone.",2005.14133v2
2021-05-02,Steady state entanglement of distant nitrogen-vacancy centers in a coherent thermal magnon bath,"We investigate steady-state entanglement (SSE) between two nitrogen-vacancy
(NV) centers in distant nanodiamonds on an ultrathin Yttrium Iron Garnet (YIG)
strip. We determine the dephasing and dissipative interactions of the qubits
with the quanta of spin waves (magnon bath) in the YIG depending on the qubit
positions on the strip. We show that the magnon's dephasing effect can be
eliminated, and we can transform the bath into a multimode displaced thermal
state using external magnetic fields. Entanglement dynamics of the qubits in
such a displaced thermal bath have been analyzed by deriving and solving the
master equation. An additional electric field is considered to engineer the
magnon dispersion relation at the band edge to control the Markovian character
of the open system dynamics. We determine the optimum geometrical parameters of
the system of distant qubits and the YIG strip to get SSE. Furthermore,
parameter regimes for which the shared displaced magnon bath can sustain
significant SSE against the local dephasing and decoherence of NV centers to
their nuclear spin environments have been determined. Along with SSE, we
investigate the steady-state coherence (SSC) and explain the physical mechanism
of how delayed SSE appears following a rapid generation and sudden death of
entanglement using the interplay of decoherence-free subspace states, system
geometry, displacement of the thermal bath, and enhancement of the qubit
dissipation near the magnon band edge. A non-monotonic relation between bath
coherence and SSE is found, and critical coherence for maximum SSE is
determined. Our results illuminate the efficient use of system geometry, band
edge in bath spectrum, and reservoir coherence to engineer system-reservoir
interactions for robust SSE and SSC.",2105.00519v2
2022-10-15,Non-local magnon transconductance in extended magnetic insulating films.\\Part II: two-fluid behavior,"This review presents a comprehensive study of the spatial dispersion of
propagating magnons electrically emitted in extended yttrium-iron garnet (YIG)
films by the spin transfer effects across a YIG$\vert$Pt interface. Our goal is
to provide a generic framework to describe the magnon transconductance inside
magnetic films. We experimentally elucidate the relevant spectral contributions
by studying the lateral decay of the magnon signal. While most of the injected
magnons do not reach the collector, the propagating magnons can be split into
two-fluids: \textit{i)} a large fraction of high-energy magnons carrying energy
of about $k_B T_0$, where $T_0$ is the lattice temperature, with a
characteristic decay length in the sub-micrometer range, and \textit{ii)} a
small fraction of low-energy magnons, which are particles carrying energy of
about $\hbar \omega_K$, where $\omega_K/(2 \pi)$ is the Kittel frequency, with
a characteristic decay length in the micrometer range. Taking advantage of
their different physical properties, the low-energy magnons can become the
dominant fluid \textit{i)} at large spin transfer rates for the bias causing
the emission of magnons, \textit{ii)} at large distance from the emitter,
\textit{iii)} at small film thickness, or \textit{iv)} for reduced band
mismatch between the YIG below the emitter and the bulk due to variation of the
magnon concentration. This broader picture complements part I \cite{kohno_SD},
which focuses solely on the nonlinear transport properties of low-energy
magnons.",2210.08283v2
2023-08-18,"Magnon Diffusion Length and Longitudinal Spin Seebeck Effect in Vanadium Tetracyanoethylene (V[TCNE]$_x$, $x \sim 2$)","Spintronic, spin caloritronic, and magnonic phenomena arise from complex
interactions between charge, spin, and structural degrees of freedom that are
challenging to model and even more difficult to predict. This situation is
compounded by the relative scarcity of magnetically-ordered materials with
relevant functionality, leaving the field strongly constrained to work with a
handful of well-studied systems that do not encompass the full phase space of
phenomenology predicted by fundamental theory. Here we present an important
advance in this coupled theory-experiment challenge, wherein we extend existing
theories of the spin Seebeck effect (SSE) to explicitly include the
temperature-dependence of magnon non-conserving processes. This expanded theory
quantitatively describes the low-temperature behavior of SSE signals previously
measured in the mainstay material yttrium iron garnet (YIG) and predicts a new
regime for magnonic and spintronic materials that have low saturation
magnetization, $M_S$, and ultra-low damping. Finally, we validate this
prediction by directly observing the spin Seebeck resistance (SSR) in the
molecule-based ferrimagnetic semiconductor vanadium tetracyanoethylene
(V[TCNE]$_x$, $x \sim 2$). These results validate the expanded theory, yielding
SSR signals comparable in magnitude to YIG and extracted magnon diffusion
length ($\lambda_m>1$ $\mu$ m) and magnon lifetime for V[TCNE]$_x$
($\tau_{th}\approx 1-10$ $\mu$ s) exceeding YIG ($\tau_{th}\sim 10$ ns).
Surprisingly, these properties persist to room temperature despite relatively
low spin wave stiffness (exchange). This identification of a new regime for
highly efficient SSE-active materials opens the door to a new class of magnetic
materials for spintronic and magnonic applications.",2308.09752v1
2009-03-02,Magnetooptical control of light collapse in bulk Kerr media,"Magneto-optical crystals allow an efficient control of the birefringence of
light via the Cotton-Mouton and Faraday effects. These effects enable a unique
combination of adjustable linear and circular birefringence, which, in turn,
can affect the propagation of light in nonlinear Kerr media. We show
numerically that the combined birefringences can accelerate, delay, or arrest
the nonlinear collapse of (2+1)D beams, and report an experimental observation
of the acceleration of the onset of collapse in a bulk Yttrium Iron Garnet
(YIG) crystal in an external magnetic field.",0903.0373v1
2011-03-19,Spin transfer torque on magnetic insulators,"Recent experimental and theoretical studies focus on spin-mediated heat
currents at interfaces between normal metals and magnetic insulators. We
resolve conflicting estimates for the order of magnitude of the spin transfer
torque by first-principles calculations. The spin mixing conductance
G^\uparrow\downarrow of the interface between silver and the insulating
ferrimagnet Yttrium Iron Garnet (YIG) is dominated by its real part and of the
order of 10^14 \Omega^-1m^-2, i.e. close to the value for intermetallic
interface, which can be explained by a local spin model.",1103.3764v2
2011-07-06,Spin Seebeck Effect: Amplification of Spin Waves by Thermal Torque,"We observe amplification of spin-wave packets propagating along a film of
yttrium iron garnet (YIG) subject to a transverse temperature gradient. The
amplification is attributed to a spin-transfer thermal torque created by spin
currents generated by means of the spin Seebeck effect that acts on the
magnetization and opposes the relaxation. The experimental data are interpreted
with a simple theoretical model using spin-wave theory that gives an
amplification gain in very good agreement with measurements.",1107.1271v2
2013-09-11,Nanomechanical AC Susceptometry of an Individual Mesoscopic Ferrimagnet,"A novel method for simultaneous detection of both DC and time-dependent
magnetic signatures in individual mesoscopic structures has emerged from early
studies in spin mechanics. Multifrequency nanomechanical detection of AC
susceptibility and its harmonics highlights reversible nonlinearities in the
magnetization response of a single yttrium iron garnet (YIG) element,
separating them from hysteretic jumps in the DC magnetization.",1309.2965v1
2013-11-12,Nonreciprocity engineering in magnetostatic spin waves,"Magnetostatic surface spin waves (MSSW) excited from a coplanar waveguide
antenna travel in different directions with different amplitudes. This effect,
called nonreciprocity of MSSW, has been investigated by micromagnetic
simulations. The ratio of amplitude of two counter propagating spin waves, the
nonreciprocity parameter {\kappa}, is obtained for different ferromagnetic
materials, such as NiFe (Py), CoFeAl, yttrium iron garnet (YIG), and GaMnAs. A
device schematic has been proposed in which {\kappa} can be tuned to a large
value by varying simple geometrical parameters of the device.",1311.2686v1
2014-04-09,Current-induced spin torque resonance of magnetic insulators,"We formulate a theory of the AC spin Hall magnetoresistance (SMR) in a
bilayer system consisting of a magnetic insulator such as yttrium iron garnet
(YIG) and a heavy metal such as platinum (Pt). We derive expressions for the DC
voltage generation based on the drift-diffusion spin model and quantum
mechanical boundary condition at the interface that reveal a spin torque
ferromagnetic resonance (ST-FMR). We predict that ST-FMR experiments will
reveal valuable information on the current-induced magnetization dynamics of
magnetic insulators and AC spin Hall effect.",1404.2360v2
2014-07-18,Microwave-induced spin currents in ferromagnetic-insulator|normal-metal bilayer system,"A microwave technique is employed to simultaneously examine the spin pumping
and the spin Seebeck effect processes in a YIG|Pt bilayer system. The
experimental results show that for these two processes, the spin current flows
in opposite directions. The temporal dynamics of the longitudinal spin Seebeck
effect exhibits that the effect depends on the diffusion of bulk
thermal-magnons in the thermal gradient in the
ferromagnetic-insulator|normal-metal system.",1407.4957v2
2015-06-09,Identification of spin wave modes strongly coupled to a co-axial cavity,"We demonstrate, at room temperature, the strong coupling of the fundamental
and non-uniform magnetostatic modes of an yttrium iron garnet (YIG)
ferrimagnetic sphere to the electromagnetic modes of a co-axial cavity. The
well-defined field profile within the cavity yields a specific coupling
strength for each magnetostatic mode. We experimentally measure the coupling
strength for the different magnetostatic modes and, by calculating the expected
coupling strengths, are able to identify the modes themselves.",1506.02902v1
2015-09-15,Magnetic Nernst effect,"The thermodynamics of irreversible processes in continuous media predicts the
existence of a Magnetic Nernst effect that results from a magnetic analog to
the Seebeck effect in a ferromagnet and magnetophoresis occurring in a
paramagnetic electrode in contact with the ferromagnet. Thus, a voltage that
has DC and AC components is expected across a Pt electrode as a response to the
inhomogeneous magnetic induction field generated by magnetostatic waves of an
adjacent YIG slab subject to a temperature gradient. The voltage frequency and
dependence on the orientation of the applied magnetic induction field are quite
distinct from that of spin pumping.",1509.04440v1
2017-02-02,Magnon Condensation and Spin Superfluidity,"We consider the phenomenon of Bose-Einstein condensation of quasi-equilibrium
magnons which leads to a spin superfluidity, the coherent quantum transfer of
magnetization in magnetic materials. These phenomena are beyond the classical
Landau-Lifshitz-Gilbert paradigm. The critical conditions for excited magnon
density for ferro- and antiferromagnets, bulk and thin films are estimated and
discussed. The BEC should occur in the antiferromagnetic hematite at much lower
excited magnon density compared to the ferromagnetic YIG.",1702.00846v2
2023-07-18,"Propagation of Coupled Acoustic, Electromagnetic and Spin Waves in Saturated Ferromagnetoelastic Solids","We study the propagation of plane waves in an unbounded body of a saturated
ferromagnetoelastic solid. The equations by Tiersten for small fields
superposed on finite initial fields in a saturated ferromagnetoelastic material
are employed, with their quasistatic magnetic field extended to dynamic
electric and magnetic fields for electromagnetic waves. Dispersion relations of
the plane waves are obtained. The cutoff frequencies and long wave
approximation of the dispersion curves are determined. Results show that
acoustic, electromagnetic and magnetic spin waves are coupled in such a
material. For YIG which is a cubic crystal without piezoelectric coupling, the
acoustic and electromagnetic waves are not directly coupled but they can still
interact indirectly through spin waves.",2307.09171v1
2023-12-05,Interplay between magnetism and superconductivity in a hybrid magnon-photon bilayer system,"Spin waves in magnetic films are affected by the vicinity to a
superconductor. Here we studied a bilayer stack made of an insulating Yttrium
Iron Garnet (YIG) film and a high-$T_c$ YBCO superconducting planar resonator.
We investigated the hybridization of magnon and photon modes reporting the
temperature evolution of microwave transmission spectra. Data analysis, based
on the description of magnon modes and on the Hopfield model, shows that the
magnon-photon coupling strength and the mode frequency shift can be ultimately
related to the temperature dependence of the penetration depth of YBCO.",2312.02785v2
2004-05-26,Microwave Magnetoelectric Effects in Single Crystal Bilayers of Yttrium Iron Garnet and Lead Magnesium Niobate-Lead Titanate,"The first observation of microwave magnetoelectric (ME) interactions through
ferromagnetic resonance (FMR) in bilayers of single crystal
ferromagnetic-piezoelectric oxides and a theoretical model for the effect are
presented. An electric field E produces a mechanical deformation in the
piezoelectric phase, resulting in a shift dHE in the resonance field for the
ferromagnet. The strength of ME coupling is obtained from data on dHE vs E.
Studies were performed at 9.3 GHz on bilayers of (111) yttrium iron garnet
(YIG) films and (001) lead magnesium niobate-lead titanate (PMN-PT). The
samples were positioned outside a TE102-reflection type cavity. Resonance
profiles were obtained for E = 0-8 kV/cm for both in-plane and out-of-plane
magnetic fields H. Important results are as follows. (i) The ME coupling in the
bilayers is an order of magnitude stronger than in polycrystalline composites
and is in the range 1-5.4 Oe cm/kOe, depending on the YIG film thickness. (ii)
The coupling strength is dependent on the magnetic field orientation and is
higher for out-of-plane H than for in-plane H. (iii) Estimated ME constant and
its dependence on volume ratio for the two phases are in good agreement with
the data.",0405622v1
2014-08-13,High Cooperativity Cavity QED with Magnons at Microwave Frequencies,"Using a sub-millimetre sized YIG (Yttrium Iron Garnet) sphere mounted in a
magnetic field-focusing cavity, we demonstrate an ultra-high cooperativity of
$10^5$ between magnon and photon modes at millikelvin temperatures and
microwave frequencies. The cavity is designed to act as a magnetic dipole by
using a novel multiple-post approach, effectively focusing the cavity magnetic
field within the YIG crystal with a filling factor of 3%. Coupling strength
(normal-mode splitting) of 2 GHz, (equivalent to 76 cavity linewidths or $0.3$
Hz per spin), is achieved for a bright cavity mode that constitutes about 10%
of the photon energy and shows that ultra-strong coupling is possible in spin
systems at microwave frequencies. With straight forward optimisations we
demonstrate that with that this system has the potential to reach
cooperativities of $10^7$, corresponding to a normal mode splitting of 5.2 GHz
and a coupling per spin approaching 1 Hz. We also observe a three-mode strong
coupling regime between a dark cavity mode and a magnon mode doublet pair,
where the photon-magnon and magnon-magnon couplings (normal-mode splittings)
are 143 MHz and 12.5 MHz respectively, with HWHM bandwidth of about 0.5 MHz.",1408.2905v3
2015-08-19,Independent tuning of electronic properties and induced ferromagnetism in topological insulators with heterostructure approach,"The quantum anomalous Hall effect (QAHE) has been recently demonstrated in
Cr- and V-doped three-dimensional topological insulators (TIs) at temperatures
below 100 mK. In those materials, the spins of unfilled d-electrons in the
transition metal dopants are exchange coupled to develop a long-range
ferromagnetic order, which is essential for realizing QAHE. However, the
addition of random dopants does not only introduce excess charge carriers that
require readjusting the Bi/Sb ratio, but also unavoidably introduces
paramagnetic spins that can adversely affect the chiral edge transport in QAHE.
In this work, we show a heterostructure approach to independently tune the
electronic and magnetic properties of the topological surface states in
(BixSb1-x)2Te3 without resorting to random doping of transition metal elements.
In heterostructures consisting of a thin (BixSb1-x)2Te3 TI film and yttrium
iron garnet (YIG), a high Curie temperature (~ 550 K) magnetic insulator, we
find that the TI surface in contact with YIG becomes ferromagnetic via
proximity coupling which is revealed by the anomalous Hall effect (AHE). The
Curie temperature of the magnetized TI surface ranges from 20 to 150 K but is
uncorrelated with the Bi fraction x in (BixSb1-x)2Te3. In contrast, as x is
varied, the AHE resistivity scales with the longitudinal resistivity. In this
approach, we decouple the electronic properties from the induced ferromagnetism
in TI. The independent optimization provides a pathway for realizing QAHE at
higher temperatures, which is important for novel spintronic device
applications.",1508.04719v1
2016-08-29,Sub-micrometer yttrium iron garnet LPE films with low ferromagnetic resonance losses,"Using liquid phase epitaxy (LPE) technique (111) yttrium iron garnet (YIG)
films with thicknesses of ~100 nm and surface roughnesses as low as 0.3 nm have
been grown as a basic material for spin-wave propagation experiments in
microstructured waveguides. The continuously strained films exhibit nearly
perfect crystallinity without significant mosaicity and with effective lattice
misfits of delta a(perpendicular)/a(substrate) ~10-4 and below. The
film/substrate interface is extremely sharp without broad interdiffusion layer
formation. All LPE films exhibit a nearly bulk-like saturation magnetization of
(1800+-20) Gs and an `easy cone' anisotropy type with extremely small in-plane
coercive fields <0.2 Oe. There is a rather weak in-plane magnetic anisotropy
with a pronounced six-fold symmetry observed for saturation field <1.5 Oe. No
significant out-of-plane anisotropy is observed, but a weak dependence of the
effective magnetization on the lattice misfit is detected. The narrowest
ferromagnetic resonance linewidth is determined to be 1.4 Oe @ 6.5 GHz which is
the lowest value reported so far for YIG films of 100 nm thicknesses and below.
The Gilbert damping coefficient for investigated LPE films is estimated to be
close to 1 x 10-4.",1608.08043v1
2017-02-17,Spin conductance of YIG thin films driven from thermal to subthermal magnons regime by large spin-orbit torque,"We report a study on spin conductance in ultra-thin films of Yttrium Iron
Garnet (YIG), where spin transport is provided by propagating spin waves, that
are generated and detected by direct and inverse spin Hall effects in two Pt
wires deposited on top. While at low current the spin conductance is dominated
by transport of thermal magnons, at high current, the spin conductance is
dominated by low-damping non-equilibrium magnons thermalized near the spectral
bottom by magnon-magnon interaction, with consequent a sensitivity to the
applied magnetic field and a longer decay length. This picture is supported by
microfocus Brillouin Light Scattering spectroscopy.",1702.05226v3
2017-06-14,Nonlocal magnon-polaron transport in yttrium iron garnet,"The spin Seebeck effect (SSE) is observed in magnetic insulator|heavy metal
bilayers as an inverse spin Hall effect voltage under a temperature gradient.
The SSE can be detected nonlocally as well, viz. in terms of the voltage in a
second metallic contact (detector) on the magnetic film, spatially separated
from the first contact that is used to apply the temperature bias (injector).
Magnon-polarons are hybridized lattice and spin waves in magnetic materials,
generated by the magnetoelastic interaction. Kikkawa et al. [Phys. Rev. Lett.
\textbf{117}, 207203 (2016)] interpreted a resonant enhancement of the local
SSE in yttrium iron garnet (YIG) as a function of the magnetic field in terms
of magnon-polaron formation. Here we report the observation of magnon-polarons
in \emph{nonlocal} magnon spin injection/detection devices for various
injector-detector spacings and sample temperatures. Unexpectedly, we find that
the magnon-polaron resonances can suppress rather than enhance the nonlocal
SSE. Using finite element modelling we explain our observations as a
competition between the SSE and spin diffusion in YIG. These results give
unprecedented insights into the magnon-phonon interaction in a key magnetic
material.",1706.04373v1
2017-08-06,Electric-field-induced extremely large change in resistance in graphene ferromagnets,"A colossal magnetoresistance ($\sim 100\times10^3\%$) and an extremely large
magnetoresistance ($\sim 1\times10^6\%$) have been previously explored in
manganite perovskites and Dirac materials, respectively. However, the
requirement of an extremely strong magnetic field (and an extremely low
temperature) makes them not applicable for realistic devices. In this work, we
propose a device that can generate even larger changes in resistance in a
zero-magnetic field and at a high temperature. The device is composed of a
graphene under two strips of yttrium iron garnet (YIG), where two gate voltages
are applied to cancel the heavy charge doping in the YIG-induced half-metallic
ferromagnets. By calculations using the Landauer-B\""{u}ttiker formalism, we
demonstrate that, when a proper gate voltage is applied on the free
ferromagnet, changes in resistance up to $305\times10^6\%$ ($16\times10^3\%$)
can be achieved at the liquid helium (nitrogen) temperature and in a zero
magnetic field. We attribute such a remarkable effect to a gate-induced
full-polarization reversal in the free ferromagnet, which results in a
metal-state to insulator-state transition in the device. We also find that, the
proposed effect can be realized in devices using other magnetic insulators such
as EuO and EuS. Our work should be helpful for developing a realistic switching
device that is energy saving and CMOS-technology compatible.",1708.01858v2
2017-09-19,Criteria for accurate determination of the magnon relaxation length from the nonlocal spin Seebeck effect,"The nonlocal transport of thermally generated magnons not only unveils the
underlying mechanism of the spin Seebeck effect, but also allows for the
extraction of the magnon relaxation length ($\lambda_m$) in a magnetic
material, the average distance over which thermal magnons can propagate. In
this study, we experimentally explore in yttrium iron garnet (YIG)/platinum
systems much further ranges compared with previous investigations. We observe
that the nonlocal SSE signals at long distances ($d$) clearly deviate from a
typical exponential decay. Instead, they can be dominated by the nonlocal
generation of magnon accumulation as a result of the temperature gradient
present away from the heater, and decay geometrically as $1/d^2$. We emphasize
the importance of looking only into the exponential regime (i.e., the
intermediate distance regime) to extract $\lambda_m$. With this principle, we
study $\lambda_m$ as a function of temperature in two YIG films which are 2.7
and 50 $\mu$m in thickness, respectively. We find $\lambda_m$ to be around 15
$\mu$m at room temperature and it increases to 40 $\mu$m at $T=$ 3.5 K. Finite
element modeling results agree with experimental studies qualitatively, showing
also a geometrical decay beyond the exponential regime. Based on both
experimental and modeling results we put forward a general guideline for
extracting $\lambda_m$ from the nonlocal spin Seebeck effect.",1709.06321v1
2018-06-04,Large spin-mixing conductance in highly Bi-doped Cu thin films,"Spin Hall effect provides an efficient tool for the conversion of a charge
current into a spin current, opening the possibility of producing pure spin
currents in non-magnetic materials for the next generation of spintronics
devices. In this sense, giant Spin Hall Effect has been recently reported in Cu
doped with 0.5 % Bi grown by sputtering and larger values are expected for
larger Bi doping, according to first principles calculations. In this work we
demonstrate the possibility of doping Cu with up to 10 % of Bi atoms without
evidences of Bi surface segregation or cluster formation, as studied by
different microscopic and spectroscopic techniques. In addition, YIG/BiCu
structures have been grown, showing a spin mixing conductance larger that the
one shown by similar Pt/YIG structures. These results reflects the potentiality
of these new materials in spintronics devices.",1806.01394v2
2019-05-29,Coherent long-range transfer of angular momentum between magnon Kittel modes by phonons,"We report ferromagnetic resonance in the normal configuration of an
electrically insulating magnetic bilayer consisting of two yttrium iron garnet
(YIG) films epitaxially grown on both sides of a 0.5-mm-thick nonmagnetic
gadolinium gallium garnet (GGG) slab. An interference pattern is observed and
it is explained as the strong coupling of the magnetization dynamics of the two
YIG layers either in phase or out of phase by the standing transverse sound
waves, which are excited through a magnetoelastic interaction. This coherent
mediation of angular momentum by circularly polarized phonons through a
nonmagnetic material over macroscopic distances can be useful for future
information technologies.",1905.12523v3
2019-09-30,Switching the Optical Chirality in Magneto-plasmonic Metasurfaces Using Applied Magnetic Fields,"Chiral nanophotonic devices are promising candidates for chiral molecules
sensing, polarization diverse nanophotonics and display technologies. Active
chiral nanophotonic devices, where the optical chirality can be controlled by
an external stimulus has triggered great research interest. However, efficient
modulation of the optical chirality has been challenging. Here, we demonstrate
switching of the extrinsic chirality by applied magnetic fields in a
magneto-plasmonic metasurface device based on a magneto-optical oxide material,
Ce1Y2Fe5O12 (Ce:YIG). Thanks to the low optical loss and strong magneto-optical
effect of Ce:YIG, we experimentally demonstrated a giant and continuous
far-field circular dichroism (CD) modulation by applied magnetic fields from
-0.65{\deg} to +1.9{\deg} at 950 nm wavelength under glancing incident
conditions. The far field CD modulation is due to both magneto-optical circular
dichroism and near-field modulation of the superchiral fields by applied
magnetic fields. Finally, we demonstrate magnetic field tunable chiral imaging
in millimeter-scale magneto-plasmonic metasurfaces fabricated using
self-assembly. Our results provide a new way for achieving planar integrated,
large-scale and active chiral metasurfaces for polarization diverse
nanophotonics.",1909.13605v1
2019-10-19,Propagation of spin-waves packets in individual nano-sized yttrium iron garnet magnonic conduits,"Modern-days CMOS-based computation technology is reaching its fundamental
limitations. The emerging field of magnonics, which utilizes spin waves for
data transport and processing, proposes a promising path to overcome these
limitations. Different devices have been demonstrated recently on the macro-
and microscale, but the feasibility of the magnonics approach essentially
relies on the scalability of the structure feature size down to an extent of a
few 10 nm, which are typical sizes for the established CMOS technology. Here,
we present a study of propagating spin-wave packets in individual yttrium iron
garnet (YIG) conduits with lateral dimensions down to 50 nm. Space and time
resolved micro-focused Brillouin-Light-Scattering (BLS) spectroscopy is used to
characterize the YIG nanostructures and measure the spin-wave decay length and
group velocity directly. The revealed magnon transport at the scale comparable
to the scale of CMOS proves the general feasibility of a magnon-based data
processing.",1910.08801v2
2020-02-27,High-temperature Anomalous Hall Effect in Transition Metal Dichalcogenide-Ferromagnetic Insulator Heterostructure,"Integration of transition metal dichalcogenides (TMDs) on ferromagnetic
materials (FM) may yield fascinating physics and promise for electronics and
spintronic applications. In this work, high-temperature anomalous Hall effect
(AHE) in the TMD ZrTe2 thin film using heterostructure approach by depositing
it on ferrimagnetic insulator YIG (Y3Fe5O12, yttrium iron garnet) is
demonstrated. In this heterostructure, significant anomalous Hall effect can be
observed at temperatures up to at least 400 K, which is a record high
temperature for the observation of AHE in TMDs, and the large RAHE is more than
one order of magnitude larger than those previously reported value in
topological insulators or TMDs based heterostructures. The magnetization of
interfacial reaction-induced ZrO2 between YIG and ZrTe2 is believed to play a
crucial role for the induced high-temperature anomalous Hall effect in the
ZrTe2. These results reveal a promising system for the room-temperature
spintronic device applications, and it may also open a new avenue toward
introducing magnetism to TMDs and exploring the quantum AHE at higher
temperatures considering the prediction of nontrivial topology in ZrTe2.",2002.12068v1
2020-06-18,Current-induced in-plane magnetization switching in biaxial ferrimagnetic insulator,"Ferrimagnetic insulators (FiMI) have been intensively used in microwave and
magneto-optical devices as well as spin caloritronics, where their
magnetization direction plays a fundamental role on the device performance. The
magnetization is generally switched by applying external magnetic fields. Here
we investigate current-induced spin-orbit torque (SOT) switching of the
magnetization in Y3Fe5O12 (YIG)/Pt bilayers with in-plane magnetic anisotropy,
where the switching is detected by spin Hall magnetoresistance. Reversible
switching is found at room temperature for a threshold current density of 10^7
A cm^-2. The YIG sublattices with antiparallel and unequal magnetic moments are
aligned parallel or antiparallel to the direction of current pulses, which is
consistent to the Neel order switching in antiferromagnetic system. It is
proposed that such a switching behavior may be triggered by the
antidamping-torque acting on the two antiparallel sublattices of FiMI. Our
finding not only broadens the magnetization switching by electrical means and
promotes the understanding of magnetization switching, but also paves the way
for all-electrically modulated microwave devices and spin caloritronics with
low power consumption.",2006.10313v1
2020-07-31,Manipulating the photonic Hall effect with hybrid Mie-exciton resonances,"We examine the far-field optical response, under-plane wave excitation in the
presence of a static magnetic field, of core-shell nanoparticles involving a
gyroelectric component, either as the inner or the outer layer, through
analytic calculations based on appropriately extended Mie theory. We focus on
absorption and scattering of light by bismuth-substituted yttrium iron garnet
(Bi:YIG) nanospheres and nanoshells, combined with excitonic materials such as
organic-molecule aggregates or two-dimensional transition-metal
dichalcogenides, and discuss the hybrid character of the modes emerging from
the coupling of the two constituents. We observe the excitation of strong
magneto-optic phenomena and explore, in particular, the response and tunability
of a magneto-transverse light current, indicative of the photonic Hall effect.
We show how interaction between the Bi:YIG and excitonic layers leads to a pair
of narrow bands of highly directional scattering, emerging from the
aforementioned hybridization, which can be tuned at will by adjusting the
geometrical or optical parameters of the system. Our theoretical study
introduces optically anisotropic media as promising templates for strong
coupling in nanophotonics, offering a means to combine tunable magnetic and
optical properties, with potential implications both in the design of
all-dielectric photonic devices but also in novel clinical applications.",2007.16062v2
2020-08-21,Magnons Parametric Pumping in Bulk Acoustic Waves Resonator,"We report on the experimental observation of excitation and detection of
parametric spin waves and spin currents in the bulk acoustic wave resonator.
The hybrid resonator consists of ZnO piezoelectric film, yttrium iron garnet
(YIG) films on gallium gadolinium garnet substrate, and a heavy metal Pt layer.
Shear bulk acoustic waves are electrically excited in the ZnO layer due to
piezoeffect at the resonant frequencies of the resonator. The magnetoelastic
interaction in the YIG film emerges magnons (spin waves) excitation by acoustic
waves either on resonator's eigenfrequencies or the half-value frequencies at
supercritical power. We investigate acoustic pumping of magnons at the
half-value frequencies and acoustic spin pumping from parametric magnons, using
the inverse spin Hall effect in the Pt layer. The constant electric voltage in
the Pt layer, depending on the frequency, the magnetic field, and the pump
power, was systematically studied. We explain the low threshold obtained (~0.4
mW) by the high efficiency of electric power transmission into the acoustic
wave in the resonator.",2008.09520v1
2020-08-29,Unveiling the polarity of the spin-to-charge current conversion in $Bi_2Se_3$,"We report an investigation of the spin- to charge-current conversion in
sputter-deposited films of topological insulator $Bi_2Se_{3}$ onto single
crystalline layers of YIG $(Y_{3}Fe_{5}O_{12})$ and polycrystalline films of
Permalloy $(Py = Ni_{81}Fe_{19})$. Pure spin current was injected into the
$Bi_{2}Se_{3}$ layer by means of the spin pumping process in which the spin
precession is obtained by exciting the ferromagnetic resonance of the
ferromagnetic film. The spin-current to charge-current conversion, occurring at
the $Bi_{2}Se_{3}/$ferromagnet interface, was attribute to the inverse
Rashba-Edelstein effect (IREE). By analyzing the data as a function of the
$Bi_{2}Se_{3}$ thickness we calculated the IREE length used to characterize the
efficiency of the conversion process and found that 1.2 pm
$\leq|{\lambda}_{IREE}|\leq$ 2.2 pm. These results support the fact that the
surface states of $Bi_{2}Se_{3}$ have a dominant role in the spin-charge
conversion process, and the mechanism based on the spin diffusion process plays
a secondary role. We also discovered that the spin- to charge-current mechanism
in $Bi_{2}Se_{3}$ has the same polarity as the one in Ta, which is the opposite
to the one in Pt. The combination of the magnetic properties of YIG and Py,
with strong spin-orbit coupling and dissipationless surface states
topologically protected of $Bi_{2}Se_{3}$ might lead to spintronic devices with
fast and efficient spin-charge conversion.",2008.12900v1
2021-07-14,Frequency fluctuations of ferromagnetic resonances at milliKelvin temperatures,"Unwanted fluctuations over time, in short, noise, are detrimental to device
performance, especially for quantum coherent circuits. Recent efforts have
demonstrated routes to utilizing magnon systems for quantum technologies, which
are based on interfacing single magnons to superconducting qubits. However, the
coupling of several components often introduces additional noise to the system,
degrading its coherence. Researching the temporal behavior can help to identify
the underlying noise sources, which is a vital step in increasing coherence
times and the hybrid device performance. Yet, the frequency noise of the
ferromagnetic resonance (FMR) has so far been unexplored. Here, we investigate
such FMR frequency fluctuations of a YIG sphere down to mK-temperatures, and
find them independent of temperature and drive power. This suggests that the
measured frequency noise in YIG is dominated by so far undetermined noise
sources, which properties are not consistent with the conventional model of
two-level systems, despite their effect on the sample linewidth. Moreover, the
functional form of the FMR frequency noise power spectral density (PSD) cannot
be described by a simple power law. By employing time-series analysis, we find
a closed function for the PSD that fits our observations. Our results underline
the necessity of coherence improvements to magnon systems for useful
applications in quantum magnonics.",2107.06531v1
2021-08-25,Quantum network with magnonic and mechanical nodes,"A quantum network consisting of magnonic and mechanical nodes connected by
light is proposed. Recent years have witnessed a significant development in
cavity magnonics based on collective spin excitations in ferrimagnetic
crystals, such as yttrium iron garnet (YIG). Magnonic systems are considered to
be a promising building block for a future quantum network. However, a major
limitation of the system is that the coherence time of the magnon excitations
is limited by their intrinsic loss (typically in the order of 1 $\mu$s for
YIG). Here, we show that by coupling the magnonic system to a mechanical system
using optical pulses, an arbitrary magnonic state (either classical or quantum)
can be transferred to and stored in a distant long-lived mechanical resonator.
The fidelity depends on the pulse parameters and the transmission loss. We
further show that the magnonic and mechanical nodes can be prepared in a
macroscopic entangled state. These demonstrate the quantum state transfer and
entanglement distribution in such a novel quantum network of magnonic and
mechanical nodes. Our work shows the possibility to connect two separate fields
of optomagnonics and optomechanics, and to build a long-distance quantum
network based on magnonic and mechanical systems.",2108.11156v3
2021-12-20,Spin current transport in hybrid Pt / multifunctional magnetoelectric Ga0.6Fe1.4O3 bilayers,"The low power manipulation of magnetization is currently a highly
sought-after objective in spintronics. Non ferromagnetic large spin-orbit
coupling heavy metal (NM) / ferromagnet (FM) heterostructures offer interesting
elements of response to this issue, by granting the manipulation of the FM
magnetization by the NM spin Hall effect (SHE) generated spin current.
Additional functionalities, such as the electric field control of the spin
current generation, can be offered using multifunctional ferromagnets. We have
studied the spin current transfer processes between Pt and the multifunctional
magnetoelectric Ga0.6Fe1.4O3 (GFO). In particular, via angular dependent
magnetotransport measurements, we were able to differentiate between magnetic
proximity effect (MPE)-induced anisotropic magnetoresistance (AMR) and spin
Hall magnetoresistance (SMR). Our analysis shows that SMR is the dominant
phenomenon at all temperatures and is the only one to be considered near room
temperature, with a magnitude comparable to those observed in Pd/YIG or Pt/YIG
heterostructures. These results indicate that magnetoelectric GFO thin films
show promises for achieving an electric-field control of the spin current
generation in NM/FM oxide-based heterostructures.",2112.10406v1
2022-02-06,Enhancing Perpendicular Magnetic Anisotropy in Garnet Ferrimagnet by Interfacing with Few-Layer WTe2,"Engineering magnetic anisotropy in a ferro- or ferrimagnetic (FM) thin film
is crucial in spintronic device. One way to modify the magnetic anisotropy is
through the surface of the FM thin film. Here, we report the emergence of a
perpendicular magnetic anisotropy (PMA) induced by interfacial interactions in
a heterostructure comprised of a garnet ferrimagnet, Y3Fe5O12 (YIG), and the
low-symmetry, high spin orbit coupling (SOC) transition metal dichalcogenide,
WTe2. At the same time, we also observed an enhancement in Gilbert damping in
the WTe2 covered YIG area. Both the magnitude of interface-induced PMA and the
Gilbert damping enhancement have no observable WTe2 thickness dependence down
to single quadruple-layer, indicating that the interfacial interaction plays a
critical role. The ability of WTe2 to enhance the PMA in FM thin film, combined
with its previously reported capability to generate out-of-plane damping like
spin torque, makes it desirable for magnetic memory applications.",2202.02834v1
2022-02-25,Direct probing of strong magnon-photon coupling in a planar geometry,"We demonstrate direct probing of strong magnon-photon coupling using
Brillouin light scattering spectroscopy in a planar geometry. The magnonic
hybrid system comprises a split-ring resonator loaded with epitaxial yttrium
iron garnet thin films of 200 nm and 2.46 $\mu$m thickness. The Brillouin light
scattering measurements are combined with microwave spectroscopy measurements
where both biasing magnetic field and microwave excitation frequency are
varied. The cooperativity for the 200 nm-thick YIG films is 4.5, and larger
cooperativity of 137.4 is found for the 2.46 $\mu$m-thick YIG film. We show
that Brillouin light scattering is advantageous for probing the magnonic
character of magnon-photon polaritons, while microwave absorption is more
sensitive to the photonic character of the hybrid excitation. A miniaturized,
planar device design is imperative for the potential integration of magnonic
hybrid systems in future coherent information technologies, and our results are
a first stepping stone in this regard. Furthermore, successfully detecting the
magnonic hybrid excitation by Brillouin light scattering is an essential step
for the up-conversion of quantum signals from the optical to the microwave
regime in hybrid quantum systems.",2202.12696v1
2022-06-27,Thermal spin current generation in the multifunctional ferrimagnet Ga$_{0.6}$Fe$_{1.4}$O$_{3}$,"In recent years, multifunctional materials have attracted increasing interest
for magnetic memories and energy harvesting applications. Magnetic insulating
materials are of special interest for this purpose, since they allow the design
of more efficient devices due to the lower Joule heat losses. In this context,
Ga$_{0.6}$Fe$_{1.4}$O$_3$ (GFO) is a good candidate for spintronics
applications, since it can exhibit multiferroicity and presents a spin Hall
magnetoresistance similar to the one observed in a yttrium iron garnet (YIG)/Pt
bilayer. Here, we explore GFO utilizing thermo-spin measurements in an on-chip
approach. By carefully considering the geometry of our thermo-spin devices we
are able to quantify the spin Seebeck effect and the spin current generation in
a GFO/Pt bilayer, obtaining a value comparable to that of YIG/Pt. This further
confirms the promises of an efficient spin current generation with the
possibility of an electric-field manipulation of the magnetic properties of the
system in an insulating ferrimagnetic material.",2206.13426v2
2022-11-16,Detection sensitivity enhancement of magnon Kerr nonlinearity in cavity magnonics induced by coherent perfect absorption,"We show how to enhance the detection sensitivity of magnon Kerr nonlinearity
(MKN) in cavity magnonics. The considered cavity-magnon system consists of a
three-dimensional microwave cavity containing two yttrium iron garnet (YIG)
spheres, where the two magnon modes (one has the MKN, while the other is
linear) in YIG spheres are simultaneously coupled to microwave photons. To
obtain the effective gain of the cavity mode, we feed two input fields into the
cavity. By choosing appropriate parameters, the coherent perfect absorption of
the two input fields occurs, and the cavity-magnon system can be described by
an effective non-Hermitian Hamiltonian. Under the pseudo-Hermitian conditions,
the effective Hamiltonian can host the third-order exceptional point (EP3),
where the three eigenvalues of the Hamiltonian coalesce into one. When the
magnon frequency shift $\Delta_K$ induced by the MKN is much smaller than the
linewidths $\Gamma$ of the peaks in the transmission spectrum of the cavity
(i.e., $\Delta_K\ll \Gamma$), the magnon frequency shift can be amplified by
the EP3, which can be probed via the output spectrum of the cavity. The scheme
we present provides an alternative approach to measure the MKN in the region
$\Delta_K\ll \Gamma$ and has potential applications in designing low-power
nonlinear devices based on the MKN.",2211.08922v2
2022-12-22,Spin wave dispersion of ultra-low damping hematite ($α\text{-Fe}_2\text{O}_3$) at GHz frequencies,"Low magnetic damping and high group velocity of spin waves (SWs) or magnons
are two crucial parameters for functional magnonic devices. Magnonics research
on signal processing and wave-based computation at GHz frequencies focussed on
the artificial ferrimagnetic garnet Y$_3$Fe$_5$O$_{12}$ (YIG) so far. We report
on spin-wave spectroscopy studies performed on the natural mineral hematite
($\alpha\text{-Fe}_2\text{O}_3$) which is a canted antiferromagnet. By means of
broadband GHz spectroscopy and inelastic light scattering, we determine a
damping coefficient of $1.1\times10^{-5}$ and magnon group velocities of a few
10 km/s, respectively, at room temperature. Covering a large regime of wave
vectors up to $k\approx 24~{\rm rad}/\mu$m, we find the exchange stiffness
length to be relatively short and only about 1 \r{A}. In a small magnetic field
of 30 mT, the decay length of SWs is estimated to be 1.1 cm similar to the best
YIG. Still, inelastic light scattering provides surprisingly broad and partly
asymmetric resonance peaks. Their characteristic shape is induced by the large
group velocities, low damping and distribution of incident angles inside the
laser beam. Our results promote hematite as an alternative and sustainable
basis for magnonic devices with fast speeds and low losses based on a stable
natural mineral.",2212.11887v2
2023-02-02,Ultrastrong Magnon-Photon Coupling Achieved by Magnetic Films in Contact with Superconducting Resonators,"Coherent coupling between spin wave excitations (magnons) and microwave
photons in a cavity may disclose new paths to unconventional phenomena as well
as for novel applications. Here, we present a systematic investigation on YIG
(Yttrium Iron Garnet) films on top of coplanar waveguide resonators made of
superconducting YBCO. We first show that spin wave excitations with frequency
higher than the Kittel mode can be excited by putting in direct contact a
5~$\mu$m thick YIG film with the YBCO coplanar resonator (cavity frequency
$\omega_c/2 \pi = 8.65$~GHz). With this configuration, we obtain very large
values of the collective coupling strength $\lambda/2 \pi \approx 2$~GHz and
cooperativity $C=5 \times 10^4$. Transmission spectra are analyzed by a
modified Hopfield model for which we provide an exact solution that allows us
to well reproduce spectra by introducing a limited number of free parameters.
It turns out that the coupling of the dominant magnon mode with photons exceeds
0.2 times the cavity frequency, thus demonstrating the achievement of the
ultrastrong coupling regime with this architecture. Our analysis also shows a
vanishing contribution of the diamagnetic term which is a peculiarity of pure
spin systems.",2302.00804v2
2023-02-10,Laser-induced magnonic band gap formation and control in YIG/GaAs heterostructure,"We demonstrate the laser-induced control over spin-wave (SW) transport in the
magnonic crystal (MC) waveguide formed from the semiconductor slab placed on
the ferrite film. We considered bilayer MC with periodical grooves performed on
the top of the n-type gallium arsenide slab side that oriented to the yttrium
iron garnet film. To observe the appearance of magnonic gap induced by laser
radiation, the fabricated structure was studied by the use of microwave
spectroscopy and Brillouin light-scattering. We perform detailed numerical
studies of this structure. We showed that the optical control of the magnonic
gaps (frequency width and position) is related to the variation of the charge
carriers' concentration in GaAs. We attribute these to nonreciprocity of SW
transport in the layered structure. Nonreciprocity was induced by the laser
exposure of the GaAs slab due to SWs' induced electromagnetic field screening
by the optically-generated charge carriers. We showed that SW dispersion,
nonreciprocity, and magnonic band gap position and width in the
ferrite-semiconductor magnonic crystal can be modified in a controlled manner
by laser radiation. Our results show the possibility of the integration of
magnonics and semiconductor electronics on the base of YIG/GaAs structures.",2302.05310v1
2023-11-29,Nonlinear erasing of propagating spin-wave pulses in thin-film Ga:YIG,"Nonlinear phenomena are key for magnon-based information processing, but the
nonlinear interaction between two spin-wave signals requires their
spatio-temporal overlap which can be challenging for directional processing
devices. Our study focuses on a gallium-substituted yttrium iron garnet film,
which exhibits an exchange-dominated dispersion relation and thus provides a
particularly broad range of group velocities compared to pure YIG. Using time-
and space-resolved Brillouin light scattering spectroscopy, we demonstrate the
excitation of time-separated spin-wave pulses at different frequencies from the
same source, where the delayed pulse catches up with the previously excited
pulse and outruns it due to its higher group velocity. By varying the
excitation power of the faster pulse, the outcome can be finely tuned from a
linear superposition to a nonlinear interaction of both pulses, resulting in a
full attenuation of the slower pulse. Therefore, our findings demonstrate the
all-magnonic erasing process of a propagating magnonic signal, which enables
the realization of complex temporal logic operations with potential
application, e.g., in inhibitory neuromorphic functionalities.",2311.17821v2
2024-01-19,Nonreciprocal Pancharatnam-Berry Metasurface for Unidirectional Wavefront Manipulation,"Optical metasurfaces have been widely used for manipulating electromagnetic
waves due to their low intrinsic loss and easy fabrication. The metasurfaces
employing the Pancharatnam-Berry (PB) geometric phase, called PB metasurfaces,
have been extensively applied to realize spin-dependent functionalities, such
as beam steering, focusing, holography, etc. The demand for PB metasurfaces in
complex environments has brought about one challenging problem, i.e., the
interference of multiple wave channels that limits the performance of PB
metasurfaces. A promising solution is developing nonreciprocal PB metasurfaces
that can isolate undesired wave channels and exhibit unidirectional
functionalities. Here, we propose a mechanism to realize nonreciprocal PB
metasurfaces of subwavelength thickness by using the magneto-optical effect of
YIG material in synergy with the PB geometric phase of spatially rotating
meta-atoms. Using full-wave numerical simulations, we show that the metasurface
composed of dielectric cylinders and a thin YIG layer can achieve nearly 92%
and 81% isolation of circularly polarized lights at 5.5 GHz and 6.5 GHz,
respectively, attributed to the enhancement of the magneto-optical effect by
the resonant Mie modes and Fabry-P\'erot cavity mode. In addition, the
metasurface can enable efficient unidirectional wavefront manipulations of
circularly polarized lights, including nonreciprocal beam steering and
nonreciprocal beam focusing. The proposed metasurface can find highly useful
applications in optical communications, optical sensing, and quantum
information processing.",2401.10772v2
2017-08-06,Thermally Driven Long Range Magnon Spin Currents in Yttrium Iron Garnet due to Intrinsic Spin Seebeck Effect,"The longitudinal spin Seebeck effect refers to the generation of a spin
current when heat flows across a normal metal/magnetic insulator interface.
Until recently, most explanations of the spin Seebeck effect use the
interfacial temperature difference as the conversion mechanism between heat and
spin fluxes. However, recent theoretical and experimental works claim that a
magnon spin current is generated in the bulk of a magnetic insulator even in
the absence of an interface. This is the so-called intrinsic spin Seebeck
effect. Here, by utilizing a non-local spin Seebeck geometry, we provide
additional evidence that the total magnon spin current in the ferrimagnetic
insulator yttrium iron garnet (YIG) actually contains two distinct terms: one
proportional to the gradient in the magnon chemical potential (pure magnon spin
diffusion), and a second proportional to the gradient in magnon temperature
($\nabla T_m$). We observe two characteristic decay lengths for magnon spin
currents in YIG with distinct temperature dependences: a temperature
independent decay length of ~ 10 ${\mu}$m consistent with earlier measurements
of pure ($\nabla T_m = 0$) magnon spin diffusion, and a longer decay length
ranging from about 20 ${\mu}$m around 250 K and exceeding 80 ${\mu}$m at 10 K.
The coupled spin-heat transport processes are modeled using a finite element
method revealing that the longer range magnon spin current is attributable to
the intrinsic spin Seebeck effect ($\nabla T_m \neq 0$), whose length scale
increases at lower temperatures in agreement with our experimental data.",1708.01941v3
2020-08-29,Exploring a quantum-information-relevant magnonic material: Ultralow damping at low temperature in the organic ferrimagnet V[TCNE]x,"Quantum information science and engineering requires novel low-loss magnetic
materials for magnon-based quantum-coherent operations. The search for low-loss
magnetic materials, traditionally driven by applications in microwave
electronics near room-temperature, has gained additional constraints from the
need to operate at cryogenic temperatures for many applications in quantum
information science and technology. Whereas yttrium iron garnet (YIG) has been
the material of choice for decades, the emergence of molecule-based materials
with robust magnetism and ultra-low damping has opened new avenues for
exploration. Specifically, thin-films of vanadium tetracyanoethylene (V[TCNE]x)
can be patterned into the multiple, connected structures needed for hybrid
quantum elements and have shown room-temperature Gilbert damping ({\alpha} = 4
\times 10^-5) that rivals the intrinsic (bulk) damping otherwise seen only in
highly-polished YIG spheres (far more challenging to integrate into arrays).
Here, we present a comprehensive and systematic study of the low-temperature
magnetization dynamics for V[TCNE]x thin films, with implications for their
application in quantum systems. These studies reveal a temperature-driven,
strain-dependent magnetic anisotropy that compensates the thin-film shape
anisotropy, and the recovery of a magnetic resonance linewidth at 5 K that is
comparable to room-temperature values (roughly 2 G at 9.4 GHz). We can account
for these variations of the V[TCNE]x linewidth within the context of scattering
from very dilute paramagnetic impurities, and anticipate additional linewidth
narrowing as the temperature is further reduced.",2008.13061v3
2022-10-15,Non-local magnon transconductance in extended magnetic insulating films.\\ Part I: spin diode effect,"This review provides a comprehensive study of the nonlinear transport
properties of magnons, which are electrically emitted or absorbed inside
extended YIG films by spin transfer effects via a YIG$\vert$Pt interface. Our
purpose is to experimentally elucidate the pertinent picture behind the
asymmetric electrical variation of the magnon transconductance analogous to an
electric diode. The feature is rooted in the variation of the density of
low-lying spin excitations via an electrical shift of the magnon chemical
potential. As the intensity of the spin transfer increases in the forward
direction (regime of magnon emission), the transport properties of low-energy
magnon go through 3 distinct regimes: \textit{i)} at low currents, where the
spin current is a linear function of the electrical current, the spin transport
is ballistic and set by the film thickness; \textit{ii)} for amplitudes of the
order of the damping compensation threshold, it switches to a highly correlated
regime limited by magnon-magnon relaxation process and marked by a saturation
of the magnon transconductance. Here the main bias, that controls the magnon
density, are thermal fluctuations beneath the emitter. \textit{iii)} As the
temperature under the emitter approaches the Curie temperature, scattering with
high-energy magnons dominates, leading to diffusive transport. We note that
such sequence of transport regimes bears analogy with electron hydrodynamic
transport in ultra-pure media predicted by Radii Gurzhi. This study restricted
to low energy part of the magnon manifold complements part II of this
review\cite{kohno_2F}, which concentrates instead on the whole spectrum of
propagating magnons.",2210.08304v2
1997-10-07,Macroscopic Quantum Tunneling of Ferromagnetic Domain Walls,"Quantum tunneling of domain walls out of an impurity potential in a
mesoscopic ferromagnetic sample is investigated. Using improved expressions for
the domain wall mass and for the pinning potential, we find that the cross-over
temperature between thermal activation and quantum tunneling is of a different
functional form than found previously. In materials like Ni or YIG, the
crossover temperatures are around 5 mK. We also find that the WKB exponent is
typically two orders of magnitude larger than current estimates. The sources
for these discrepancies are discussed, and precise estimates for the transition
from three-dimensional to one-dimensional magnetic behavior of a wire are
given. The cross-over temperatures from thermal to quantum transitions and
tunneling rates are calculated for various materials and sample sizes.",9710064v1
2009-06-29,A Magnetization Sensitive Potential at Garnet-Metal Interfaces,"We investigate a magnetization-dependent voltage that appears at the
interface between garnets and various metals. The voltage is even in the
applied magnetic field and is dependent on the surface roughness and the
pressure holding the surfaces together. Large variations in the size, sign and
magnetic dependence are observed between different metal surfaces. Some
patterns have been identified in the measured voltages and a simple model is
described that can accommodate the gross features. The bulk magnetoelectric
response of one of our polycrystalline YIG samples is measured and is found to
be consistent with a term in the free energy that is quadratic in both the
electric and magnetic fields. However, the presence of such a term does not
fully explain the complex magnetization dependence of the measured voltages.",0906.5340v2
2010-08-27,Enhancement of the spin pumping efficiency by spin-wave mode selection,"The spin pumping efficiency of lateral standing spin wave modes in a
rectangular YIG/Pt sample has been investigated by means of the inverse
spin-Hall effect (ISHE). The standing spin waves drive spin pumping, the
generation of spin currents from magnetization precession, into the Pt layer
which is converted into a detectable voltage due to the ISHE. We discovered
that the spin pumping efficiency is significantly higher for lateral standing
surface spin waves rather than for volume spin wave modes. The results suggest
that the use of higher-mode surface spin waves allows for the fabrication of an
efficient spin-current injector.",1008.4714v2
2011-12-21,Direct detection of magnon spin transport by the inverse spin Hall effect,"Conversion of traveling magnons into an electron carried spin current is
demonstrated in a time resolved experiment using a spatially separated
inductive spin-wave source and an inverse spin Hall effect (ISHE) detector. A
short spin-wave packet is excited in a yttrium-iron garnet (YIG) waveguide by a
microwave signal and is detected at a distance of 3 mm by an attached Pt layer
as a delayed ISHE voltage pulse. The delay in the detection appears due to the
finite spin-wave group velocity and proves the magnon spin transport. The
experiment suggests utilization of spin waves for the information transfer over
macroscopic distances in spintronic devices and circuits.",1112.4969v1
2013-02-06,Theory of spin Hall magnetoresistance,"We present a theory of the spin Hall magnetoresistance (SMR) in multilayers
made from an insulating ferromagnet F, such as yttrium iron garnet (YIG), and a
normal metal N with spin-orbit interactions, such as platinum (Pt). The SMR is
induced by the simultaneous action of spin Hall and inverse spin Hall effects
and therefore a non-equilibrium proximity phenomenon. We compute the SMR in
F$|$N and F$|$N$|$F layered systems, treating N by spin-diffusion theory with
quantum mechanical boundary conditions at the interfaces in terms of the
spin-mixing conductance. Our results explain the experimentally observed spin
Hall magnetoresistance in N$|$F bilayers. For F$|$N$|$F spin valves we predict
an enhanced SMR amplitude when magnetizations are collinear. The SMR and the
spin-transfer torques in these trilayers can be controlled by the magnetic
configuration.",1302.1352v1
2013-02-27,Specific heat and thermal conductivity of ferromagnetic magnons in Yttrium Iron Garnet,"The specific heat and thermal conductivity of the insulating ferrimagnet
Y$_3$Fe$_5$O$_{12}$ (Yttrium Iron Garnet, YIG) single crystal were measured
down to 50 mK. The ferromagnetic magnon specific heat $C$$_m$ shows a
characteristic $T^{1.5}$ dependence down to 0.77 K. Below 0.77 K, a downward
deviation is observed, which is attributed to the magnetic dipole-dipole
interaction with typical magnitude of 10$^{-4}$ eV. The ferromagnetic magnon
thermal conductivity $\kappa_m$ does not show the characteristic $T^2$
dependence below 0.8 K. To fit the $\kappa_m$ data, both magnetic defect
scattering effect and dipole-dipole interaction are taken into account. These
results complete our understanding of the thermodynamic and thermal transport
properties of the low-lying ferromagnetic magnons.",1302.6739v1
2013-05-14,Exchange magnetic field torques in YIG/Pt bilayers observed by the spin-Hall magnetoresistance,"The effective field torque of an yttrium-iron-garnet film on the spin
accumulation in an attached Pt film is measured by the spin-Hall
magnetoresistance (SMR). As a result, the magnetization direction of a
ferromagnetic insulating layer can be measured electrically. Experimental
transverse and longitudinal resistances are well described by the theoretical
model of SMR in terms of the direct and inverse spin-Hall effect, for different
Pt thicknesses [3, 4, 8 and 35nm]. Adopting a spin-Hall angle of Pt
$\theta_{SH}=0.08$, we obtain the spin diffusion length of Pt
($\lambda=1.1\pm0.3$nm) as well as the real
($G_r=(7\pm3)\times10^{14}\Omega^{-1}$m$^{-2}$) and imaginary part
($G_i=(5\pm3)\times10^{13}\Omega^{-1}$m$^{-2}$) of the spin-mixing conductance
and their ratio ($G_r/G_i=16\pm4$).",1305.3117v2
2013-07-29,Current-induced spin wave excitation in Pt|YIG bilayer,"We develop a self-consistent theory for current-induced spin wave excitations
in normal metal-magnetic insulator bilayer systems, thereby establishing the
relation between spin wave excitation and the experimentally controlled
parameters. We fully take into account the complex spin wave spectrum including
dipolar interactions and surface anisotropy as well as the spin-pumping at the
interface. Our results focus on the mode-dependent power close to the critical
currents for spin wave excitation. The major findings are (a) the spin transfer
torque can excite different spin-wave modes simultaneously; (b) spin pumping
counterbalances spin-transfer torque and affects the surface modes more than
the bulk modes; (c) spin pumping inhibits high frequency spin-wave modes,
thereby redshifting the excitation spectrum. We can get agreement with
experiments on yttrium iron garnet|platinum bilayers by postulating the
existence of surface anisotropy modes.",1307.7607v2
2014-04-14,Sign of inverse spin Hall voltages generated by ferromagnetic resonance and temperature gradients in yttrium iron garnet|platinum bilayers,"We carried out a concerted effort to determine the absolute sign of the
inverse spin Hall effect voltage generated by spin currents injected into a
normal metal. We focus on yttrium iron garnet (YIG)|platinum bilayers at room
temperature, generating spin currents by microwaves and temperature gradients.
We find consistent results for different samples and measurement setups that
agree with theory. We suggest a right-hand-rule to define a positive spin Hall
angle corresponding to with the voltage expected for the simple case of
scattering of free electrons from repulsive Coulomb charges.",1404.3490v2
2014-05-16,Damping of Confined Modes in a Ferromagnetic Thin Insulating Film: Angular Momentum Transfer Across a Nanoscale Field-defined Interface,"We observe a dependence of the damping of a confined mode of precessing
ferromagnetic magnetization on the size of the mode. The micron-scale mode is
created within an extended, unpatterned YIG film by means of the intense local
dipolar field of a micromagnetic tip. We find that damping of the confined mode
scales like the surface-to-volume ratio of the mode, indicating an interfacial
damping effect (similar to spin pumping) due to the transfer of angular
momentum from the confined mode to the spin sink of ferromagnetic material in
the surrounding film. Though unexpected for insulating systems, the measured
intralayer spin-mixing conductance $g_{\uparrow \downarrow} = 5.3 \times
10^{19} {\rm m}^{-2}$ demonstrates efficient intralayer angular momentum
transfer.",1405.4203v2
2014-05-28,Electronic control of the spin-wave damping in a magnetic insulator,"It is demonstrated that the decay time of spin-wave modes existing in a
magnetic insulator can be reduced or enhanced by injecting an in-plane dc
current, $I_\text{dc}$, in an adjacent normal metal with strong spin-orbit
interaction. The demonstration rests upon the measurement of the ferromagnetic
resonance linewidth as a function of $I_\text{dc}$ in a 5~$\mu$m diameter
YIG(20nm){\textbar}Pt(7nm) disk using a magnetic resonance force microscope
(MRFM). Complete compensation of the damping of the fundamental mode is
obtained for a current density of $\sim 3 \cdot 10^{11}\text{A.m}^{-2}$, in
agreement with theoretical predictions. At this critical threshold the MRFM
detects a small change of static magnetization, a behavior consistent with the
onset of an auto-oscillation regime.",1405.7415v1
2014-10-02,Simultaneous detection of the spin-Hall magnetoresistance and the spin-Seebeck effect in Platinum and Tantalum on Yttrium Iron Garnet,"The spin-Seebeck effect (SSE) in platinum (Pt) and tantalum (Ta) on yttrium
iron garnet (YIG) has been investigated by both externally heating the sample
(using an on-chip Pt heater on top of the device) as well as by current-induced
heating. For SSE measurements, external heating is the most common method to
obtain clear signals. Here we show that also by current-induced heating it is
possible to directly observe the SSE, separate from the also present spin-Hall
magnetoresistance (SMR) signal, by using a lock-in detection technique. Using
this measurement technique, the presence of additional 2nd order signals at low
applied magnetic fields and high heating currents is revealed. These signals
are caused by current-induced magnetic fields (Oersted fields) generated by the
used AC-current, resulting in dynamic SMR signals.",1410.0551v2
2015-05-07,Formation of Bright Solitons from Wave Packets with Repulsive Nonlinearity,"Formation of bright envelope solitons from wave packets with a repulsive
nonlinearity was observed for the first time. The experiments used surface
spin-wave packets in magnetic yttrium iron garnet (YIG) thin film strips. When
the wave packets are narrow and have low power, they undergo self-broadening
during the propagation. When the wave packets are relatively wide or their
power is relatively high, they can experience self-narrowing or even evolve
into bright solitons. The experimental results were reproduced by numerical
simulations based on a modified nonlinear Schr\""odinger equation model.",1505.01882v1
2015-05-26,Observation of pure inverse spin Hall effect in ferromagnetic metals by FM/AFM exchange bias structures,"We report that the spin current generated by spin Seebeck effect (SSE) in
yttrium iron garnet (YIG) can be detected by a ferromagnetic metal (NiFe). By
using the FM/AFM exchange bias structure (NiFe/IrMn), inverse spin Hall effect
(ISHE) and planar Nernst effect (PNE) of NiFe can be unambiguously separated,
allowing us to observe a pure ISHE signal. After eliminating the in plane
temperature gradient in NiFe, we can even observe a pure ISHE signal without
PNE from NiFe itself. It is worth noting that a large spin Hall angle (0.098)
of NiFe is obtained, which is comparable with Pt. This work provides a kind of
FM/AFM exchange bias structures to detect the spin current by charge signals,
and highlights ISHE in ferromagnetic metals can be used in spintronic research
and applications.",1505.06911v2
2015-06-17,Magnetic field control of the spin Seebeck effect,"The origin of the suppression of the longitudinal spin Seebeck effect by
applied magnetic fields is studied. We perform numerical simulations of the
stochastic Landau-Lifshitz-Gilbert equation of motion for an atomistic spin
model and calculate the magnon accumulation in linear temperature gradients for
different strengths of applied magnetic fields and different length scales of
the temperature gradient. We observe a decrease of the magnon accumulation with
increasing magnetic field and we reveal that the origin of this effect is a
field dependent change of the frequency distribution of the propagating
magnons. With increasing field the magnonic spin currents are reduced due to a
suppression of parts of the frequency spectrum. By comparison with measurements
of the magnetic field dependent longitudinal spin Seebeck effect in YIG thin
films with various thicknesses, we find that our model describes the
experimental data very well, demonstrating the importance of this effect for
experimental systems.",1506.05290v1
2015-06-19,All electrical coherent control of the magnetization in thin Yittrium Iron Garnet film,"We demonstrate coherent control of time domain ferromagnetic resonance by all
electrical excitation and detection. Using two ultrashort magnetic field steps
with variable time delay we control the induction decay in yttrium iron garnet
(YIG). By setting suitable delay times between the two steps the precession of
the magnetization can either be enhanced or completely stopped. The method
allows for a determination of the precession frequency within a few precession
periods and with an accuracy much higher than can be achieved using fast
fourier transformation. Moreover it holds the promise to massively increase
precession amplitudes in pulsed inductive microwave magnetometry (PIMM) using
low amplitude finite pulse trains. Our experiments are supported by
micromagnetic simulations which nicely confirm the experimental results.",1506.05935v1
2015-08-20,Superstrong Coupling of a Microwave Cavity to YIG Magnons,"Multiple-post reentrant 3D lumped cavity modes have been realized to design
the concept of discrete Whispering Gallery and Fabry-Perot-like Modes for
multimode microwave Quantum Electrodynamics experiments. Using a magnon
spin-wave resonance of a submillimeter-sized Yttrium-Iron-Garnet sphere at
milliKelvin temperatures and a four-post cavity, we demonstrate the
ultra-strong coupling regime between discrete Whispering Gallery Modes and a
magnon resonance with strength of 1.84 GHz. By increasing the number of posts
to eight and arranging them in a D$_4$ symmetry pattern, we expand the mode
structure to that of a discrete Fabry-Perot cavity and modify the Free Spectral
Range (FSR). We reach the superstrong coupling regime, where spin-photon
coupling strength is larger than FSR, with coupling strength in the 1.1 to 1.5
GHz range.",1508.04967v3
2015-08-25,Non-local magnetoresistance in YIG/Pt nanostructures,"We study the local and non-local magnetoresistance of thin Pt strips
deposited onto yttrium iron garnet. The local magnetoresistive response,
inferred from the voltage drop measured along one given Pt strip upon
current-biasing it, shows the characteristic magnetization orientation
dependence of the spin Hall magnetoresistance. We simultaneously also record
the non-local voltage appearing along a second, electrically isolated, Pt
strip, separated from the current carrying one by a gap of a few 100 nm. The
corresponding non-local magnetoresistance exhibits the symmetry expected for a
magnon spin accumulation-driven process, confirming the results recently put
forward by Cornelissen et al. [1]. Our magnetotransport data, taken at a series
of different temperatures as a function of magnetic field orientation, rotating
the externally applied field in three mutually orthogonal planes, show that the
mechanisms behind the spin Hall and the non-local magnetoresistance are
qualitatively different. In particular, the non-local magnetoresistance
vanishes at liquid Helium temperatures, while the spin Hall magnetoresistance
prevails.",1508.06130v1
2015-09-14,Spectral characteristics of time resolved magnonic spin Seebeck effect,"Spin Seebeck effect (SSE) holds promise for new spintronic devices with
low-energy consumption. The underlying physics, essential for a further
progress, is yet to be fully clarified. This study of the time resolved
longitudinal SSE in the magnetic insulator yttrium iron garnet (YIG) concludes
that a substantial contribution to the spin current stems from small
wave-vector subthermal exchange magnons. Our finding is in line with the recent
experiment by S. R. Boona and J. P. Heremans, Phys. Rev. B 90, 064421 (2014).
Technically, the spin-current dynamics is treated based on the
Landau-Lifshitz-Gilbert (LLG) equation also including magnons back-action on
thermal bath, while the formation of the time dependent thermal gradient is
described self-consistently via the heat equation coupled to the magnetization
dynamics",1509.04018v1
2015-11-24,Ferromagnetic Resonance of a YIG film in the Low Frequency Regime,"An improved method for characterizing the magnetic anisotropy of films with
cubic symmetry is described and is applied to an yttrium iron garnet (111)
film. Analysis of the FMR spectra performed both in-plane and out-of-plane from
0.7 to 8 GHz yielded the magnetic anisotropy constants as well as the
saturation magnetization. The field at which FMR is observed turns out to be
quite sensitive to anisotropy constants (by more than a factor ten) in the low
frequency (< 2 GHz) regime and when the orientation of the magnetic field is
nearly normal to the sample plane; the restoring force on the magnetization
arising from the magnetocrystalline anisotropy fields is then comparable to
that from the external field, thereby allowing the anisotropy constants to be
determined with greater accuracy. In this region, unusual dynamical behaviors
are observed such as multiple resonances and a switching of FMR resonance with
only a 1 degree change in field orientation at 0.7 GHz.",1511.07892v1
2015-12-04,Magnetic field dependence of the magnon spin diffusion length in the magnetic insulator yttrium iron garnet,"We investigated the effect of an external magnetic field on the diffusive
spin transport by magnons in the magnetic insulator yttrium iron garnet (YIG),
using a non-local magnon transport measurement geometry. We observed a decrease
in magnon spin diffusion length $\lambda_m$ for increasing field strengths,
where $\lambda_m$ is reduced from 9.6$\pm1.2$ $\mu$m at 10 mT to 4.2$\pm0.6$
$\mu$m at 3.5 T at room temperature. In addition, we find that there must be at
least one additional transport parameter that depends on the external magnetic
field. Our results do not allow us to unambiguously determine whether this is
the magnon equilibrium density or the magnon diffusion constant. These results
are significant for experiments in the more conventional longitudinal spin
Seebeck geometry, since the magnon spin diffusion length sets the length scale
for the spin Seebeck effect as well and is relevant for its understanding.",1512.01410v1
2016-01-21,Spin pumping in strongly coupled magnon-photon systems,"We experimentally investigate magnon-polaritons, arising in ferrimagnetic
resonance experiments in a microwave cavity with a tuneable quality factor. To
his end, we simultaneously measure the electrically detected spin pumping
signal and microwave reflection (the ferrimagnetic resonance signal) of a
yttrium iron garnet (YIG) / platinum (Pt) bilayer in the microwave cavity. The
coupling strength of the fundamental magnetic resonance mode and the cavity is
determined from the microwave reflection data. All features of the magnetic
resonance spectra predicted by first principle calculations and an input-output
formalism agree with our experimental observations. By changing the decay rate
of the cavity at constant magnon-photon coupling rate, we experimentally tune
in and out of the strong coupling regime and successfully model the
corresponding change of the spin pumping signal. Furthermore, we observe the
coupling and spin pumping of several spin wave modes and provide a quantitative
analysis of their coupling rates to the cavity.",1601.05681v1
2016-02-04,Investigation of the unidirectional spin heat conveyer effect in a 200nm thin Yttrium Iron Garnet film,"We have investigated the unidirectional spin wave heat conveyer effect in
sub-micron thick yttrium iron garnet (YIG) films using lock-in thermography
(LIT). Although the effect is small in thin layers this technique allows us to
observe asymmetric heat transport by magnons which leads to asymmetric
temperature profiles differing by several mK on both sides of the exciting
antenna, respectively. Comparison of Damon-Eshbach and backward volume modes
shows that the unidirectional heat flow is indeed due to non-reciprocal
spin-waves. Because of the finite linewidth, small asymmetries can still be
observed when only the uniform mode of ferromagnetic resonance is excited. The
latter is of extreme importance for example when measuring the inverse
spin-Hall effect because the temperature differences can result in
thermovoltages at the contacts. Because of the non-reciprocity these
thermovoltages reverse their sign with a reversal of the magnetic field which
is typically deemed the signature of the inverse spin-Hall voltage.",1602.01662v1
2016-03-14,Spin Hall Effect Induced Spin Transfer Through an Insulator,"When charge current passes through a normal metal that exhibits spin Hall
effect, spin accumulates at the edge of the sample in the transverse direction.
We predict that this spin accumulation, or spin voltage, enables quantum
tunneling of spin through an insulator or vacuum to reach a ferromagnet without
transferring charge. In a normal metal/insulator/ferromagnetic insulator
trilayer (such as Pt/oxide/YIG), the quantum tunneling explains the
spin-transfer torque and spin pumping that exponentially decay with the
thickness of the insulator. In a normal metal/insulator/ferromagnetic metal
trilayer (such as Pt/oxide/Co), the spin transfer in general does not decay
monotonically with the thickness of the insulator. Combining with the spin Hall
magnetoresistance, this tunneling mechanism points to the possibility of a new
type of tunneling spectroscopy that can probe the magnon density of states of a
ferromagnetic insulator in an all-electrical and noninvasive manner.",1603.04240v2
2016-05-01,Magnetoelectric fields for microwave chirality discrimination in enantiomeric liquids,"Chirality discrimination is of a fundamental interest in biology, chemistry,
and metamaterial studies. In optics, near-field plasmon-resonance spectroscopy
with superchiral probing fields is effectively applicable for analyses of large
biomolecules with chiral properties. We show possibility for microwave
near-field chirality discrimination analysis based on magnon-resonance
spectroscopy. Newly developed capabilities in microwave sensing using
magnetoelectric (ME) probing fields originated from multiresonance
magnetic-dipolar-mode (MDM) oscillations in quasi-2D yttrium-iron-garnet (YIG)
disks, provide a potential for unprecedented measurements of chemical and
biological objects. We report on microwave near-field chirality discrimination
for aqueous D- and L-glucose solutions. The shown ME-field sensing is addressed
to microwave biomedical diagnostics and pathogen detection and to deepening our
understanding of microwave-biosystem interactions. It can be also important for
an analysis and design of microwave chiral metamaterials.",1605.00212v1
2016-05-30,"An integrated approach to doped thin films with strain tunable magnetic anisotropy: Powder synthesis, target preparation and pulsed laser deposition of Bi:YIG","We present a synthesis/processing method for fabricating ferrimagnetic
insulator (Bi-doped yttrium iron garnet) thin films with tunable magnetic
anisotropy. Since the desired magnetic properties rely on controllable
thickness and successful doping, we pay attention to the entire
synthesis/processing procedure (nanopowder synthesis, nanocrystalline target
preparation and pulsed laser deposition (PLD)). Atomically flat films were
deposited by PLD on (111)-orientated yttrium aluminum garnet. We show a
significant enhancement of perpendicular anisotropy in the films, caused by
strain-induced anisotropy. In addition, the perpendicular anisotropy is tunable
by decreasing the film thickness and overwhelms the shape anisotropy at a
critical thickness of 3.5 nm.",1605.09084v2
2016-06-10,Indirect Coupling between Two Cavity Photon Systems via Ferromagnetic Resonance,"We experimentally realize indirect coupling between two cavity modes via
strong coupling with the ferromagnetic resonance in Yttrium Iron Garnet (YIG).
We find that some indirectly coupled modes of our system can have a higher
microwave transmission than the individual uncoupled modes. Using a coupled
harmonic oscillator model, the influence of the oscillation phase difference
between the two cavity modes on the nature of the indirect coupling is
revealed. These indirectly coupled microwave modes can be controlled using an
external magnetic field or by tuning the cavity height. This work has potential
for use in controllable optical devices and information processing
technologies.",1606.03469v1
2016-07-08,Magnon Polarons in the Spin Seebeck Effect,"Sharp structures in magnetic field-dependent spin Seebeck effect (SSE)
voltages of Pt/Y$_{3}$Fe$_{5}$O$_{12}$ (YIG) at low temperatures are attributed
to the magnon-phonon interaction. Experimental results are well reproduced by a
Boltzmann theory that includes the magnetoelastic coupling (MEC). The SSE
anomalies coincide with magnetic fields tuned to the threshold of
magnon-polaron formation. The effect gives insight into the relative quality of
the lattice and magnetization dynamics.",1607.02312v2
2016-07-12,Effect of Quantum Tunneling on Spin Hall Magnetoresistance,"We present a formalism that simultaneously incorporates the effect of quantum
tunneling and spin diffusion on spin Hall magnetoresistance observed in normal
metal/ferromagnetic insulator bilayers (such as Pt/YIG) and normal
metal/ferromagnetic metal bilayers (such as Pt/Co), in which the angle of
magnetization influences the magnetoresistance of the normal metal. In the
normal metal side the spin diffusion is known to affect the landscape of the
spin accumulation caused by spin Hall effect and subsequently the
magnetoresistance, while on the ferromagnet side the quantum tunneling effect
is detrimental to the interface spin current which also affects the spin
accumulation. The influence of generic material properties such as spin
diffusion length, layer thickness, interface coupling, and insulating gap can
be quantified in a unified manner, and experiments that reveal the quantum
feature of the magnetoresistance are suggested.",1607.03409v1
2016-07-13,Surface state dominated spin-charge current conversion in topological insulator/ferromagnetic insulator heterostructures,"We report the observation of ferromagnetic resonance-driven spin pumping
signals at room temperature in three-dimensional topological insulator thin
films -- Bi2Se3 and (Bi,Sb)2Te3 -- deposited by molecular beam epitaxy on
yttrium iron garnet thin films. By systematically varying the Bi2Se3 film
thickness, we show that the spin-charge conversion efficiency, characterized by
the inverse Rashba-Edelstein effect length (lambda_IREE), increases
dramatically as the film thickness is increased from 2 quintuple layers,
saturating above 6 quintuple layers. This suggests a dominant role of surface
states in spin and charge interconversion in topological insulator/ferromagnet
heterostructures. Our conclusion is further corroborated by studying a series
of YIG/(BiSb)2Te3 heterostructures. Finally, we use the ferromagnetic resonance
linewidth broadening and the inverse Rashba-Edelstein signals to determine the
effective interfacial spin mixing conductance and lambda_IREE.",1607.03872v1
2016-08-05,On supercurrents in Bose-Einstein magnon condensates in YIG ferrimagnet,"Recently E. Sonin commented [1] on our preprint ""Supercurrent in a room
temperature Bose-Einstein magnon condensate"" [2,3], arguing that our ""claim of
detection of spin supercurrent is premature and has not been sufficiently
supported by presented experimental results and their theoretical
interpretation."" We consider the appearance of this Comment as a sign of
significant interest into the problem of supercurrents in Bose-Einstein magnon
condensates. Here, we explicitly address E. Sonin's comments and show that our
interpretation of our experimental results as a detection of a magnon
supercurrent is fully supported not only by the experimental results
themselves, but also by independent theoretical analysis [4].",1608.01813v2
2016-10-31,Strong coupling of magnons in a YIG sphere to photons in a planar superconducting resonator in the quantum limit,"We report measurements of a superconducting coplanar waveguide resonator
(CPWR) coupled to a sphere of yttrium-iron garnet. The non-uniform CPWR field
allows us to excite various magnon modes in the sphere. Mode frequencies and
relative coupling strengths are consistent with theory. Strong coupling is
observed to several modes even with, on average, less than one excitation
present in the CPWR. The time response to square pulses shows oscillations at
the mode splitting frequency. These results indicate the feasibility of
combining magnonic and planar superconducting quantum devices.",1610.09963v2
2017-01-03,Magnetic control of Goos-Hanchen shifts in a yttrium-iron-garnet film,"We investigate the Goos-Hanchen (G-H) shifts reflected and transmitted by a
yttrium-iron-garnet (YIG) film for both normal and oblique incidence. It is
found that the nonreciprocity effect of the MO material does not only result in
a nonvanishing reflected shift at normal incidence, but also leads to a
slab-thickness-independent term which breaks the symmetry between the reflected
and transmitted shifts at oblique incidence. The asymptotic behaviors of the
normal-incidence reflected shift are obtained in the vicinity of two
characteristic frequencies corresponding to a minimum reflectivity and a total
reflection, respectively. Moreover, the coexistence of two types of
negative-reflected-shift (NRS) at oblique incidence is discussed. We show that
the reversal of the shifts from positive to negative values can be realized by
tuning the magnitude of applied magnetic field, the frequency of incident wave
and the slab thickness as well as the incident angle. In addition, we further
investigate two special cases for practical purposes: the reflected shift with
a total reflection and the transmitted shift with a total transmission.
Numerical simulations are also performed to verify our analytical results.",1701.01462v2
2017-02-10,"Relative weight of the inverse spin Hall and spin rectification effects for metallic Py,Fe/Pt and insulating YIG/Pt bilayers estimated by angular dependent spin pumping measurements","We quantify the relative weight of inverse spin Hall and spin rectification
effects occurring in RF-sputtered polycrystalline permalloy, molecular beam
epitaxy-grown epitaxial iron and liquid phase epitaxy-grown yttrium-iron-garnet
bilayer systems with different capping materials. To distinguish the spin
rectification signal from the inverse spin Hall voltage the external magnetic
field is rotated in-plane to take advantage of the different angular
dependencies of the prevailing effects. We prove that in permalloy anisotropic
magnetoresistance is the dominant source for spin rectification while in
epitaxial iron the anomalous Hall effect has an also comparable strength. The
rectification in yttrium-iron-garnet/platinum bilayers reveals an angular
dependence imitating the one seen for anisotropic magnetoresistance caused by
spin Hall magnetoresistance.",1702.03119v1
2017-02-20,Parametric pumping of spin waves by acoustic waves,"The linear and nonlinear interactions between spin waves (magnons) and
acoustic waves (phonons) in magnetostrictive materials provide an exciting
opportunity for realizing novel microwave signal processing devices and
spintronic circuits. Here we demonstrate the parametric pumping of spin waves
by acoustic waves, the possibility of which has long been theoretically
anticipated but never experimentally realized. Spin waves propagating in a thin
film of yttrium iron garnet (YIG), a magnetostrictive ferrimagnet with low spin
and acoustic wave damping, are pumped using an acoustic resonator driven at
frequencies near twice the spin wave frequency. The observation of a
counter-propagating idler wave and a distinct pump threshold that increases
quadratically with frequency non-degeneracy are evidence of a nonlinear
parametric pumping process consistent with classical theory. This demonstration
of acoustic parametric pumping lays the groundwork for developing new
spintronic and microwave signal processing devices based on amplification and
manipulation of spin waves by efficient, spatially localized acoustic
transducers.",1702.06038v1
2017-03-22,Fabrication and magnetic control of Y3Fe5O12 cantilevers,"We have fabricated ferrite cantilevers in which their vibrational properties
can be controlled by external magnetic fields. Submicron-scale cantilever
structures were made from Y3Fe5O12 (YIG) films by physical etching combined
with use of a focused ion beam milling technique. We found that the cantilevers
exhibit two resonance modes which correspond to horizontal and vertical
vibrations. Under external magnetic fields, the resonance frequency of the
horizontal mode increases, while that of the vertical mode decreases,
quantitatively consistent with our numerical simulation for magnetic forces.
The changes in resonance frequencies with magnetic fields reach a few percent,
showing that efficient magnetic control of resonance frequencies was achieved.",1703.07533v1
2017-05-05,Nano-patterned magnonic crystals based on ultrathin YIG films,"We demonstrate a microscopic magnonic-crystal waveguide produced by
nano-patterning of a 20 nm thick film of Yttrium Iron Garnet. By using the
phase-resolved micro-focus Brillouin light scattering spectroscopy, we map the
intensity and the phase of spin waves propagating in such a periodic magnetic
structure. Based on these maps, we obtain the dispersion and the attenuation
characteristics of spin waves providing detailed information about the physics
of spin-wave propagation in the magnonic crystal. We show that, in contrast to
the simplified physical picture, the maximum attenuation of spin waves is
achieved close to the edge of the magnonic band gap, which is associated with
non-trivial reflection characteristics of spin waves in non-uniform field
potentials.",1705.02267v1
2017-05-06,Scaling of the spin Seebeck effect in bulk and thin film,"Whilst there have been several reports of the spin Seebeck effect to date,
comparison of the absolute voltage(s) measured, in particular for thin films,
is limited. In this letter we demonstrate normalization of the spin Seebeck
effect for Fe$_3$O$_4$:Pt thin film and YIG:Pt bulk samples with respect to the
heat flux J$_q$, and temperature difference $\Delta$T. We demonstrate that the
standard normalization procedures for these measurements do not account for an
unexpected scaling of the measured voltage with area that is observed in both
bulk and thin film. Finally, we present an alternative spin Seebeck coefficient
for substrate and sample geometry independent characterization of the spin
Seebeck effect.",1705.02491v3
2017-05-09,"Anomalous, spin, and valley Hall effects in graphene deposited on ferromagnetic substrates","Spin, anomalous, and valley Hall effects in graphene-based hybrid structures
are studied theoretically within the Green function formalism and linear
response theory. Two different types of hybrid systems are considered in
detail: (i) graphene/boron nitride/cobalt(nickel), and (ii) graphene/YIG. The
main interest is focused on the proximity-induced exchange interaction between
graphene and magnetic substrate and on the proximity-enhanced spin-orbit
coupling. The proximity effects are shown to have a significant influence on
the electronic and spin transport properties of graphene. To find the spin,
anomalous and valley Hall conductivities we employ certain effective
Hamiltonians which have been proposed recently for the hybrid systems under
considerations. Both anomalous and valley Hall conductivities have universal
values when the Fermi level is inside the energy gap in the electronic
spectrum.",1705.03220v1
2017-06-06,Spin Seebeck effect and magnon-magnon drag in Pt/YIG/Pt structures,"The formation of the two: injected (""coherent"") and ""thermally"" excited,
different in energies magnon subsystems and the influence of its interaction
with phonons and between on drag effect under spin Seebeck effect conditions in
the magnetic insulator part of the metal/ferromagnetic insulator/metal
structure is studied. An approximation of the effective parameters, when each
of the interacting subsystems (""injected"", ""thermal"" magnons, and phonons) is
characterized by its own effective temperature and drift velocities have been
considered. The analysis of the macroscopic momentum balance equations of the
systems of interest conducted for different ratios of the drift velocities of
the magnon and phonon currents show that the ""injected"" magnons relaxation on
the ""thermal"" ones is possible to be dominant over its relaxation on phonons.
This interaction will be the defining in the forming of the temperature
dependence of the spin-wave current under spin Seebeck effect conditions, and
inelastic part of the magnon-magnon interaction is the dominant spin relaxation
mechanism.",1706.02154v1
2017-10-16,Positive-Negative Birefringence in Multiferroic Layered Metasurfaces,"We uncover and identify the regime for a magnetically and ferroelectrically
controllable negative refraction of light traversing multiferroic, oxide-based
metastructure consisting of alternating nanoscopic ferroelectric (SrTiO$_2$)
and ferromagnetic (Y$_3$Fe$_2$(FeO$_4$)$_3$, YIG) layers. We perform analytical
and numerical simulations based on discretized, coupled equations for the
self-consistent Maxwell/ferroelectric/ferromagnetic dynamics and obtain a
biquadratic relation for the refractive index. Various scenarios of ordinary
and negative refraction in different frequency ranges are analyzed and
quantified by simple analytical formula that are confirmed by full-fledge
numerical simulations. Electromagnetic-waves injected at the edges of the
sample are propagated exactly numerically. We discovered that for particular
GHz frequencies, waves with different polarizations are characterized by
different signs of the refractive index giving rise to novel types of phenomena
such as a positive-negative birefringence effect, and magnetically controlled
light trapping and accelerations.",1710.05995v1
2017-10-18,Strong Coupling of 3D Cavity Photons to Travelling Magnons At Low Temperatures,"We demonstrate strong coupling between travelling magnons in an Yttrium Iron
Garnet film and 3D microwave cavity photons at milli-Kelvin temperatures. The
coupling strength of $350$MHz or $7.3$\% of resonance frequency is observed.
The magnonic subsystem is represented by the Damon-Eshbach magnetostatic
surface wave with a distribution of wave numbers giving the linewidth of 15MHz.
The ways to improve this parameter are discussed. The energy gap in the
spectrum given by the Zeeman energy and the shape-anisotropy energy in the film
geometry give rise to a significant asymmetry of the double peak structure of
the photon-magnon avoided level crossing. A structure of two parallel YIG films
is investigated using the same re-entrant magnetostatic surface wave transducer
revealing a higher order magnon modes existing in both films. Combination of a
multi-post re-entrant cavity and multiple films is a potential base for
engineering both magnon and photon spectra.",1710.06601v1
2017-11-01,Spin current noise of the spin Seebeck effect and spin pumping,"We theoretically investigate the fluctuation of a pure spin current induced
by the spin Seebeck effect and spin pumping in a normal metal (NM)/ferromagnet
(FM) bilayer system. Starting with a simple FI--NM interface model with both
spin-conserving and spin-non-conserving processes, we derive general
expressions of the spin current and the spin-current noise at the interface
within second-order perturbation of the FI--NM coupling strength, and estimate
them for an yttrium iron garnet (YIG) --platinum interface. We show that the
spin-current noise can be used to determine the effective spin carried by a
magnon, modified by the spin-non-conserving process at the interface. In
addition, we show that it provides information on the effective spin of a
magnon, heating at the interface under spin pumping, and spin Hall angle of the
NM.",1711.00237v2
2017-12-11,Predicting the Spin Seebeck Voltage in Spin-polarized Materials: A Quantum Mechanical Transport Model Approach,"The spin Seebeck effect has recently been demonstrated as a viable method of
direct energy conversion that has potential to outperform energy conversion
from the conventional Seebeck effect. In this study, a computational transport
model is developed and validated that predicts the spin Seebeck voltage in
spin-polarized materials using material parameter obtain from first principle
ground state density functional calculations. The transport model developed is
based on a 1D effective mass description coupled with a microscopic inverse
spin Hall relationship. The model can predict both the spin current and voltage
generated in a non-magnetic material placed on top of a ferromagnetic material
in a transverse spin Seebeck configuration. The model is validated and verified
with available experimental data of La:YIG. Future applications of this model
include the high-throughput exploration of new spin-based thermoelectric
materials.",1712.04074v1
2018-01-09,Negative spin Hall magnetoresistance in antiferromagnetic Cr2O3/Ta bilayer at low temperature region,"We investigate the observation of negative spin Hall magnetoresistance (SMR)
in antiferromagnetic Cr2O3/Ta bilayers at low temperature. The sign of the SMR
signals is changed from positive to negative monotonously from 300 K to 50 K.
The change of the signs for SMR is related with the competitions between the
surface ferromagnetism and bulky antiferromagnetic of Cr2O3. The surface
magnetizations of Cr2O3 (0001) is considered to be dominated at higher
temperature, while the bulky antiferromagnetics gets to be robust with
decreasing of temperature. The slopes of the abnormal Hall curves coincide with
the signs of SMR, confirming variational interface magnetism of Cr2O3 at
different temperature. From the observed SMR ratio under 3 T, the spin mixing
conductance at Cr2O3/Ta interface is estimated to be 1.12*10^14 (ohm^-1*m^-2),
which is comparable to that of YIG/Pt structures and our early results of
Cr2O3/W. (Appl. Phys. Lett. 110, 262401 (2017))",1801.02747v1
2018-04-08,Optical cooling of magnons,"Inelastic scattering of light by spin waves generates an energy flow between
the light and magnetization fields, a process that can be enhanced and
controlled by concentrating the light in magneto-optical resonators. Here, we
model the cooling of a sphere made of a magnetic insulator, such as yttrium
iron garnet (YIG), using a monochromatic laser source. When the magnon
lifetimes are much larger than the optical ones, we can treat the latter as a
Markovian bath for magnons. The steady-state magnons are canonically
distributed with a temperature that is controlled by the light intensity. We
predict that such a cooling process can significantly reduce the temperature of
the magnetic order within current technology.",1804.02683v1
2018-04-10,Microwave cavity tuned with liquid metal and its application to Electron Paramagnetic Resonance,"This note presents a method to tune the resonant frequency $f_{0}$ of a
rectangular microwave cavity. This is achieved using a liquid metal, GaInSn, to
decrease the volume of the cavity. It is possible to shift $f_{0}$ by filling
the cavity with this alloy, in order to reduce the relative distance between
the internal walls. The resulting modes have resonant frequencies in the range
$7\div8\,$GHz. The capability of the system of producing an Electron
Paramagnetic Resonance (EPR) measurement has been tested by placing a 1 mm
diameter Yttrium Iron Garnet (YIG) sphere inside the cavity, and producing a
strong coupling between the cavity resonance and Kittel mode. This work shows
the possibility to tune a resonant system in the GHz range, which can be useful
for several applications.",1804.03443v1
2018-07-03,Spin pinning and spin-wave dispersion in nanoscopic ferromagnetic waveguides,"Spin waves are investigated in Yttrium Iron Garnet (YIG) waveguides with a
thickness of 39 nm and widths ranging down to 50 nm, i.e., with aspect ratios
thickness over width approaching unity, using Brillouin Light Scattering
spectroscopy. The experimental results are verified by a semi-analytical theory
and micromagnetic simulations. A critical width is found, below which the
exchange interaction suppresses the dipolar pinning phenomenon. This changes
the quantization criterion for the spin-wave eigenmodes and results in a
pronounced modification of the spin-wave characteristics. The presented
semi-analytical theory allows for the calculation of spin-wave mode profiles
and dispersion relations in nano-structures.",1807.01358v3
2018-07-17,Magnon-phonon conversion experiment and phonon spin,"Recent experiment demonstrates magnon to phonon conversion in a YIG film
under the application of a non-uniform magnetic field. Light scattered from
phonons is observed to change its polarization state interpreted by the authors
signifying phonon spin. In this note we argue that the experimental data merely
shows the exchange of angular momentum $\pm \hbar$ per photon. We suggest that
it has physical origin in the orbital angular momentum of phonons. The
distinction between spin and orbital parts of the total angular momentum, and
between phonons and photons with added emphasis on their polarizations is
explained. The main conclusion of the present note is that phonon spin
hypothesis is unphysical.",1807.08614v2
2018-07-31,Fresnel diffraction of spin waves,"The propagation of magnetostatic forward volume waves excited by a
constricted coplanar waveguide is studied via inductive spectroscopy
techniques. A series of devices consisting of pairs of sub-micrometer size
antennae is used to perform a discrete mapping of the spin wave amplitude in
the plane of a 30-nm thin YIG film. We found that the spin wave propagation
remains well focused in a beam shape of width comparable to the constriction
length and that the amplitude within the constriction displays oscillations,
two features which are explained in terms of near-field Fresnel diffraction
theory.",1807.11754v1
2018-08-23,First harmonic measurements of the spin Seebeck effect,"We present measurements of the spin Seebeck effect (SSE) by a technique that
combines alternating currents (AC) and direct currents (DC). The method is
applied to a ferrimagnetic insulator/heavy metal bilayer,
Y$_3$Fe$_5$O$_{12}$(YIG)/Pt. Typically, SSE measurements use an AC current to
produce an alternating temperature gradient and measure the voltage generated
by the inverse spin-Hall effect in the heavy metal at twice the AC frequency.
Here we show that when Joule heating is associated with AC and DC bias
currents, the SSE response occurs at the frequency of the AC current drive and
can be larger than the second harmonic SSE response. We compare the first and
second harmonic responses and show that they are consistent with the SSE. The
field dependence of the voltage response is used to characterize the
damping-like and field-like torques. This method can be used to explore
nonlinear thermoelectric effects and spin dynamics induced by temperature
gradients.",1808.07813v1
2018-11-29,Efficient spin transport in a paramagnetic insulator,"The discovery of new materials that efficiently transmit spin currents has
been important for spintronics and material science. The electric insulator
$\mathrm{Gd}_3\mathrm{Ga}_5\mathrm{O}_{12}$ (GGG) is a superior substrate for
growing magnetic films, but has never been considered as a conduit for spin
currents. Here we report spin current propagation in paramagnetic GGG over
several microns. Surprisingly, the spin transport persists up to temperatures
of 100 K $\gg$ $T_{\mathrm{g}} = 180$ mK, GGG's magnetic glass-like transition
temperature. At 5 K we find a spin diffusion length ${\lambda_{\mathrm{GGG}}} =
1.8 \pm 0.2 {\mu}$m and a spin conductivity ${\sigma}_{\mathrm{GGG}} = (7.3 \pm
0.3) \times10^4$ $\mathrm{Sm}^{-1}$ that is larger than that of the record
quality magnet $\mathrm{Y}_3\mathrm{Fe}_5\mathrm{O}_{12}$ (YIG). We conclude
that exchange coupling is not required for efficient spin transport, which
challenges conventional models and provides new material-design strategies for
spintronic devices.",1811.11972v1
2019-01-04,How to accurately determine a saturation magnetization of the sample in a ferromagnetic resonance experiment?,"The phenomenon of ferromagnetic resonance (FMR) is still being exploited for
determining the magnetocrystalline anisotropy constants of magnetic materials.
We show that one can also determine accurately the saturation magnetization of
the sample using results of FMR experiments after taking into account the
relationship between resonance frequency and curvature of the spatial
distribution of free energy at resonance. Specifically, three examples are
given of calculating saturation magnetization from FMR data: we use historical
Bickford's measurements from 1950 for bulk magnetite, Liu's measurements from
2007 for a 500 mn thin film of a weak ferromagnet (Ga, Mn)As, and Wang's
measurements from 2014 for an ultrathin film of YIG. In all three cases, the
magnetization values we have determined are consistent with the results of
measurements.",1901.01207v1
2019-04-08,Quantum entanglement between two magnon modes via Kerr nonlinearity,"We propose a scheme to entangle two magnon modes via Kerr nonlinear effect
when driving the systems far-from-equilibrium. We consider two macroscopic
yttrium iron garnets (YIGs) interacting with a single-mode microcavity through
the magnetic dipole coupling. The Kittel mode describing the collective
excitations of large number of spins are excited through driving cavity with a
strong microwave field. We demonstrate how the Kerr nonlineraity creates the
entangled quantum states between the two macroscopic ferromagnetic samples,
when the microcavity is strongly driven by a blue-detuned microwave field. Such
quantum entanglement survives at the steady state. Our work offers new insights
and guidance to designate the experiments for observing the entanglement in
massive ferromagnetic materials. It can also find broad applications in
macroscopic quantum effects and magnetic spintronics.",1904.04167v1
2019-08-09,Observation of anti-PT symmetry phase transition in the magnon-cavity-magnon coupled system,"As the counterpart of PT symmetry, abundant phenomena and potential
applications of anti-PT symmetry have been predicted or demonstrated
theoretically. However, experimental realization of the coupling required in
the anti-PT symmetry is difficult. Here, by coupling two YIG spheres to a
microwave cavity, the large cavity dissipation rate makes the magnons coupled
dissipatively with each other, thereby obeying a two-dimensional anti-PT
Hamiltonian. In terms of the magnon-readout method, a new method adopted here,
we demonstrate the validity of our method in constructing an anti-PT system and
present the counterintuitive level attraction process. Our work provides a new
platform to explore the anti-PT symmetry properties and paves the way to study
multi-magnoncavity-polariton systems.",1908.03358v1
2019-10-11,Simulation of sympathetic cooling an optically levitated magnetic nanoparticle via coupling to a cold atomic gas,"A proposal for cooling the translational motion of optically levitated
magnetic nanoparticles is presented. The theoretical cooling scheme involves
the sympathetic cooling of a ferromagnetic YIG nanosphere with a spin-polarized
atomic gas. Particle-atom cloud coupling is mediated through the magnetic
dipole-dipole interaction. When the particle and atom oscillations are small
compared to their separation, the interaction potential becomes dominantly
linear which allows the particle to exchange energy with the $N$ atoms. While
the atoms are continuously Doppler cooled, energy is able to be removed from
the nanoparticle's motion as it exchanges energy with the atoms. The rate at
which energy is removed from the nanoparticle's motion was studied for three
species of atoms (Dy, Cr, Rb) by simulating the full $N+1$ equations of motion
and was found to depend on system parameters with scalings that are consistent
with a simplified model. The nanoparticle's damping rate due to sympathetic
cooling is competitive with and has the potential to exceed commonly employed
cooling methods.",1910.05371v3
2019-10-30,Strong coupling-enabled broadband non-reciprocity,"Non-reciprocity of signal transmission enhances capacity of communication
channels and protects transmission quality against possible signal
instabilities, thus becoming an important component ensuring coherent
information processing. However, non-reciprocal transmission requires breaking
time-reversal symmetry (TRS) which poses challenges of both practical and
fundamental character hindering the progress. Here we report a new scheme for
achieving broadband non-reciprocity using a specially engineered hybrid
microwave cavity. The TRS breaking is realized via strong coherent coupling
between a selected chiral mode in the microwave cavity and a single collective
spin excitation (magnon) in a ferromagnetic yttrium iron garnet (YIG) sphere.
The non-reciprocity in transmission is observed spanning nearly a 0.5 GHz
frequency band, which outperforms by two orders of magnitude the previously
achieved bandwidths. Our findings open new directions for robust coherent
information processing in a broad range of systems in both classical and
quantum regimes.",1910.14117v2
2019-11-09,The magnonic superfluid droplet at room temperature,"We declare the observation of spin superfluid state in Yttrium Iron Garnet
(YIG) at room temperature. It is similar to a Homogeneous Precessing State
(HPD), observed earlier in antiferromagnetic superfluid $^3$He-B. The formation
of this state explains by the repulsive interaction between magnons, which is
required as a prior condition for the spin superfluidity. It establishes an
energy gap, which stabilizes the long range superfluid transport of
magnetization and determines the Ginzburg-Landau coherence length. This
discovery paves a way to many quantum applications of supermagnonics at room
temperature, such as magnetic Josephson effect, long distance spin transport,
Q-bit, quantum logics, magnetic sensors and others.",1911.03708v1
2019-11-26,Ultrastrong coupling between a microwave resonator and antiferromagnetic resonances of rare earth ion spins,"Quantum magnonics is a new and active research field, leveraging the strong
collective coupling between microwaves and magnetically ordered spin systems.
To date work in quantum magnonics has focused on transition metals and almost
entirely on ferromagnetic resonances in yttrium iron garnet (YIG).
Antiferromagnetic systems have gained interest as they produce no stray field,
and are therefore robust to magnetic perturbations and have narrow, shape
independent resonant linewidths. Here we show the first experimental evidence
of ultrastrong-coupling between a microwave cavity and collective
antiferromagnetic resonances (magnons) in a rare earth crystal. The combination
of the unique optical and spin properties of the rare earths and collective
antiferromagnetic order paves the way for novel quantum magnonic applications.",1911.11311v1
2019-12-05,Enhanced spin-orbit coupling in a heavy metal via molecular coupling,"Heavy metals are key to spintronics because of their high spin-orbit coupling
(SOC) leading to efficient spin conversion and strong magnetic interactions.
When C60 is deposited on Pt, the molecular interface is metallised and the spin
Hall angle in YIG/Pt increased, leading to an enhancement of up to 600% in the
spin Hall magnetoresistance and 700% for the anisotropic magnetoresistance.
This correlates with Density Functional Theory simulations showing changes of
0.46 eV/C60 in the SOC of Pt. This effect opens the possibility of gating the
molecular hybridisation and SOC of metals.",1912.02712v2
2020-02-11,Sub-micrometer near-field focusing of spin waves in ultrathin YIG films,"We experimentally demonstrate tight focusing of a spin wave beam excited in
extended nanometer-thick films of Yttrium Iron Garnet by a simple microscopic
antenna functioning as a single-slit near-field lens. We show that the focal
distance and the minimum transverse width of the focal spot can be controlled
in a broad range by varying the frequency/wavelength of spin waves and the
antenna geometry. The experimental data are in good agreement with the results
of numerical simulations. Our findings provide a simple solution for
implementation of magnonic nano-devices requiring local concentration of the
spin-wave energy.",2002.04284v1
2020-03-27,Electrical detection of unconventional transverse spin-currents in obliquely magnetized thin films,"In a typical experiment in magnonics, thin films are magnetized in-plane and
spin waves only carry angular momentum along their spatial propagation
direction. Motivated by the experiments of Bozhko et al. [Phys. Rev. Research
2, 023324 (2020)], we show theoretically that for obliquely magnetized thin
films, exchange-dipolar spin waves are accompanied by a transverse
spin-current. We propose an experiment to electrically detect this transverse
spin-current with Pt strips on top of a YIG film, by comparing the induced
spin-current for spin waves with opposite momenta. We predict the relative
difference to be of the order $10^{-4}$, for magnetic fields tilted at least
$30^{\circ}$ out of plane. This transverse spin-current is the result of the
long range dipole-dipole interaction and the inversion symmetry breaking of the
interface.",2003.12520v4
2020-03-12,"Tunable multiwindow magnomechanically induced transparency, Fano resonances, and slow-to-fast light conversion","We investigate the absorption and transmission properties of a weak probe
field under the influence of a strong control field in a hybrid cavity
magnomechanical system in the microwave regime. This hybrid system consists of
two ferromagnetic material yttrium iron garnet (YIG) spheres strongly coupled
to a single cavity mode. In addition to two magnon-induced transparency (MIT)
that arise due to strong photon-magnon interactions, we observe a
magnomechanically induced transparency (MMIT) due to the presence of nonlinear
phonon-magnon interaction. In addition, we discuss the emergence and tunability
of the multiple Fano resonances in our system. We find that due to strong
photon-magnon coupling the group delay of the probe field can be enhanced
significantly. The subluminal or superluminal propagation depends on the
frequency of the magnons, which can be easily tuned by an external bias
magnetic field. Besides, the group delay of the transmitted field can also be
controlled with the control field power.",2003.13760v4
2020-05-13,Waveguide cavity optomagnonics for broadband multimode microwave-to-optics conversion,"Cavity optomagnonics has emerged as a promising platform for studying
coherent photon-spin interactions as well as tunable microwave-to-optical
conversion. However, current implementation of cavity optomagnonics in
ferrimagnetic crystals remains orders of magnitude larger in volume than
state-of-the-art cavity optomechanical devices, resulting in very limited
magneto-optical interaction strength. Here, we demonstrate a cavity
optomagnonic device based on integrated waveguides and its application for
microwave-to-optical conversion. By designing a ferrimagnetic rib waveguide to
support multiple magnon modes with maximal mode overlap to the optical field,
we realize a high magneto-optical cooperativity which is three orders of
magnitude higher compared to previous records obtained on polished YIG spheres.
Furthermore, we achieve tunable conversion of microwave photons at around 8.45
GHz to 1550 nm light with a broad conversion bandwidth as large as 16.1 MHz.
The unique features of the system point to novel applications at the crossroad
between quantum optics and magnonics.",2005.06429v1
2020-05-18,Local spin Seebeck imaging with scanning thermal probe,"In this work we present the results of an experiment to locally resolve the
spin Seebeck effect in a high-quality Pt/YIG sample. We achieve this by
employing a locally heated scanning thermal probe to generate a highly local
non-equilibrium spin current. To support our experimental results, we also
present a model based on the non-equilibrium thermodynamic approach which is in
a good agreement with experimental findings. To further corroborate our
results, we index the locally resolved spin Seebeck effect with that of the
local magnetisation texture by MFM and correlate corresponding regions. We
hypothesise that this technique allows imaging of magnetisation textures within
the magnon diffusion length and hence characterisation of spin caloritronic
materials at the nanoscale.",2005.08539v1
2020-05-20,Frequency mixing in a ferrimagnetic sphere resonator,"Frequency mixing in ferrimagnetic resonators based on yttrium and calcium
vanadium iron garnets (YIG and CVBIG) is employed for studying their nonlinear
interactions. The ferrimagnetic Kittel mode is driven by applying a pump tone
at a frequency close to resonance. We explore two nonlinear frequency mixing
configurations. In the first one, mixing between a transverse pump tone and an
added longitudinal weak signal is explored, and the experimental results are
compared with the predictions of the Landau-Zener-Stuckelberg model. In the
second one, intermodulation measurements are employed by mixing pump and signal
tones both in the transverse direction for studying a bifurcation between a
stable spiral and a stable node attractors. Our results are applicable for
developing sensitive signal receivers with high gain for both the radio
frequency and the microwave bands.",2005.09864v1
2020-06-25,Magnon-exciton proximity coupling at a van der Waals heterointerface,"Spin and photonic systems are at the heart of modern information devices and
emerging quantum technologies. An interplay between electron-hole pairs
(excitons) in semiconductors and collective spin excitations (magnons) in
magnetic crystals would bridge these heterogeneous systems, leveraging their
individual assets in novel interconnected devices. Here, we report the
magnon-exciton coupling at the interface between a magnetic thin film and an
atomically-thin semiconductor. Our approach allies the long-lived magnons
hosted in a film of yttrium iron garnet (YIG) to strongly-bound excitons in a
flake of a transition metal dichalcogenide, MoSe$_2$. The magnons induce on the
excitons a dynamical valley Zeeman effect ruled by interfacial exchange
interactions. This nascent class of hybrid system suggests new opportunities
for information transduction between microwave and optical regions.",2006.14257v2
2020-08-04,Quantitative comparison of magnon transport experiments in three-terminal YIG/Pt nanostructures acquired via dc and ac detection techniques,"All-electrical generation and detection of pure spin currents is a promising
way towards controlling the diffusive magnon transport in magnetically ordered
insulators. We quantitatively compare two measurement schemes, which allow to
measure the magnon spin transport in a three-terminal device based on a yttrium
iron garnet thin film. We demonstrate that the dc charge current method based
on the current reversal technique and the ac charge current method utilizing
first and second harmonic lock-in detection can both efficiently distinguish
between electrically and thermally injected magnons. In addition, both
measurement schemes allow to investigate the modulation of magnon transport
induced by an additional dc charge current applied to the center modulator
strip. However, while at low modulator charge current both schemes yield
identical results, we find clear differences above a certain threshold current.
This difference originates from nonlinear effects of the modulator current on
the magnon conductance.",2008.01416v1
2020-09-09,Sub-pico-liter magneto-optical cavities,"Microwave-to-optical conversion via ferromagnetic magnons has so-far been
limited by the optical coupling rates achieved in mm-scale whispering gallery
mode resonators. Towards overcoming this limitation, we propose and demonstrate
an open magneto-optical cavity containing a thin-film of yttrium iron garnet
(YIG). We achieve a 0.1 pL (100 $\mu$m$^{3}$) optical mode volume, $\sim$50
times smaller than previous devices. From this, we estimate the magnon
single-photon coupling rate is $G\approx50$ Hz. This open cavity design offers
the prospect of wavelength scale mode volumes, small polarization splittings,
and good magneto-optical mode overlap. With achievable further improvements and
optimization, efficient microwave-optical conversion and magnon cooling devices
become a realistic possibility.",2009.04162v1
2020-10-24,Enhanced sensing of weak anharmonicities through coherences in dissipatively coupled anti-PT symmetric systems,"In the last few years, the great utility of PT-symmetric systems in sensing
small perturbations has been recognized. Here, we propose an alternate method
relevant to dissipative systems, especially those coupled to the vacuum of the
electromagnetic fields. In such systems, which typically show anti-PT symmetry
and do not require the incorporation of gain, vacuum induces coherence between
two modes. Owing to this coherence, the linear response acquires a pole on the
real axis. We demonstrate how this coherence can be exploited for the enhanced
sensing of very weak anhamonicities at low pumping rates. Higher drive powers
($\sim 0.1$ W), on the other hand, generate new domains of coherences. Our
results are applicable to a wide class of systems, and we specifically
illustrate the remarkable sensing capabilities in the context of a weakly
anharmonic Yttrium Iron Garnet (YIG) sphere interacting with a cavity via a
tapered fiber waveguide. A small change in the anharmonicity leads to a
substantial change in the induced spin current.",2010.12954v1
2020-11-16,Electrically induced strong modulation of magnons transport in ultrathin magnetic insulator films,"Magnon transport through a magnetic insulator can be controlled by
current-biased heavy-metal gates that modulate the magnon conductivity via the
magnon density. Here, we report nonlinear modulation effects in 10$\,$nm thick
yttrium iron garnet (YIG) films. The modulation efficiency is larger than
40\%/mA. The spin transport signal at high DC current density (2.2$\times
10^{11}\,$A/m$^{2}$) saturates for a 400$\,$nm wide Pt gate, which indicates
that even at high current levels a magnetic instability cannot be reached in
spite of the high magnetic quality of the films.",2011.07800v1
2020-12-01,Magnon hybridization in ferrimagnetic heterostructures,"We study magnon hybridization in a ferrimagnetic heterostructure consisting
of ultrathin gadolinium iron garnet and yttrium iron garnet layers and show the
localized and extended spatial profiles of the magnon modes with different
polarizations. These modes are expected to have distinct thermal excitation
properties in the presence of a temperature gradient across the
heterostructure. From a quantitative analysis of their consequences on
longitudinal spin Seebeck effect, we predict an observable shift of the
sign-changing temperature with respect to the one previously observed in
gadolinium iron garnet. Moreover, the sign-changing point of spin Seebeck
signal is found to be tunable by YIG thickness. Our results suggest the
necessity of taking into account the temperature difference between the magnon
modes in ferrimagnetic heterostructures.",2012.00576v1
2020-12-01,Design of an optomagnonic crystal: towards optimal magnon-photon mode matching at the microscale,"We put forward the concept of an optomagnonic crystal: a periodically
patterned structure at the microscale based on a magnetic dielectric, which can
co-localize magnon and photon modes. The co-localization in small volumes can
result in large values of the photon-magnon coupling at the single quanta
level, which opens perspectives for quantum information processing and quantum
conversion schemes with these systems. We study theoretically a simple geometry
consisting of a one-dimensional array of holes with an abrupt defect,
considering the ferrimagnet Yttrium Iron Garnet (YIG) as the basis material. We
show that both magnon and photon modes can be localized at the defect, and use
symmetry arguments to select an optimal pair of modes in order to maximize the
coupling. We show that an optomagnonic coupling in the kHz range is achievable
in this geometry, and discuss possible optimization routes in order to improve
both coupling strengths and optical losses.",2012.00760v2
2021-01-12,Temperature dependence of the mean magnon collision time in a spin Seebeck device,"Based on the relaxation time approximation, the mean collision time for
magnon scattering $\tau_c(T)$ is computed from the experimental spin Seebeck
coefficient of a bulk YIG / Pt bilayer. The scattering results to be composed
by two processes: the low temperature one, with a $T^{-1/2}$ dependence, is
attributed to the scattering by defects and provides a mean free path around 10
$\mu$m; the high temperature one, depending on $T^{-4}$, is associated to the
scattering by other magnons. The results are employed to predict the thickness
dependence of the spin Seebeck coefficient for thin films.",2101.04405v1
2021-01-25,Nonreciprocal Transmission and Entanglement in a cavity-magnomechanical system,"Quantum entanglement, a key element for quantum information is generated with
a cavity-magnomechanical system. It comprises of two microwave cavities, a
magnon mode and a vibrational mode, and the last two elements come from a YIG
sphere trapped in the second cavity. The two microwave cavities are connected
by a superconducting transmission line, resulting in a linear coupling between
them. The magnon mode is driven by a strong microwave field and coupled to
cavity photons via magnetic dipole interaction, and at the same time interacts
with phonons via magnetostrictive interaction. By breaking symmetry of the
configuration, we realize nonreciprocal photon transmission and one-way
bipartite quantum entanglement. By using current experimental parameters for
numerical simulation, it is hoped that our results may reveal a new strategy to
built quantum resources for the realization of noise-tolerant quantum
processors, chiral networks, and so on.",2101.09931v1
2021-02-24,Phase-controlled pathway interferences and switchable fast-slow light in a cavity-magnon polariton system,"We study the phase controlled transmission properties in a compound system
consisting of a 3D copper cavity and an yttrium iron garnet (YIG) sphere. By
tuning the relative phase of the magnon pumping and cavity probe tones,
constructive and destructive interferences occur periodically, which strongly
modify both the cavity field transmission spectra and the group delay of light.
Moreover, the tunable amplitude ratio between pump-probe tones allows us to
further improve the signal absorption or amplification, accompanied by either
significantly enhanced optical advance or delay. Both the phase and
amplitude-ratio can be used to realize in-situ tunable and switchable fast-slow
light. The tunable phase and amplitude-ratio lead to the zero reflection of the
transmitted light and an abrupt fast-slow light transition. Our results confirm
that direct magnon pumping through the coupling loops provides a versatile
route to achieve controllable signal transmission, storage, and communication,
which can be further expanded to the quantum regime, realizing coherent-state
processing or quantum-limited precise measurements.",2102.12181v1
2021-03-10,Experimental Demonstration of a Rowland Spectrometer for Spin Waves,"We experimentally demonstrate the operation of a spin-wave Rowland
spectrometer. In the proposed device geometry, spin waves are coherently
excited on a diffraction grating and form an interference pattern that
spatially separates spectral components of the incoming signal. The diffraction
grating was created by focused-ion-beam irradiation, which was found to locally
eliminate the ferrimagnetic properties of YIG, without removing the material.
We found that in our experiments spin waves were created by an indirect
mechanism, by exploiting nonlinear resonance between the grating and the
coplanar waveguide. Our work paves the way for complex spin-wave optic devices
-- chips that replicate the functionality of integrated optical devices on a
chip-scale.",2103.06165v1
2021-04-11,Ultrafast Measurements of the Interfacial Spin Seebeck Effect in Au and Rare-Earth Iron Garnet Bilayers,"We investigate picosecond spin-currents across Au/iron-garnet interfaces in
response to ultrafast laser heating of the electrons in the Au film. In the
picoseconds after optical heating, interfacial spin currents occur due to an
interfacial temperature difference between electrons in the metal and magnons
in the insulator. We report measurements of this interfacial longitudinal spin
Seebeck effect between Au and rare-earth iron-garnet insulators, i.e. RE$_3$
Fe$_5$O$_{12}$, where RE is Y, Eu, Tb, Tm. We use time domain thermoreflectance
(TDTR) measurements to characterize the thermal response of the bilayer to
ultrafast optical heating. We use time-resolved magneto-optic Kerr effect
(TR-MOKE) measurements of the Au layer to measure the time-evolution of spin
accumulation in the Au film. We observe a spin Seebeck effect between Au/TmIG
that is three times larger than for an Au/YIG bilayer. The interfacial thermal
conductance between electrons in the Au and magnons in the TmIG layer is ~ 3
$\frac{MW}{m^2 K}$.",2104.05075v2
2021-05-06,Spin Wave Interference Detection via Inverse Spin Hall Effect,"In this letter, we present experimental data demonstrating spin wave
interference detection using spin Hall effect (ISHE). Two coherent spin waves
are excited in a yttrium-iron garnet (YIG) waveguide by continuous microwave
signals. The initial phase difference between the spin waves is controlled by
the external phase shifter. The ISHE voltage is detected at a distance of 2 mm
and 4 mm away from the spin wave generating antennae by an attached Pt layer.
Experimental data show ISHE voltage oscillation as a function of the phase
difference between the two interfering spin waves. This experiment demonstrates
an intriguing possibility of using ISHE in spin wave logic circuit converting
spin wave phase into an electric signal",2105.02979v1
2021-06-21,A low-loss ferrite circulator as a tunable chiral quantum system,"Ferrite microwave circulators allow one to control the directional flow of
microwave signals and noise, and thus play a crucial role in present-day
superconducting quantum technology. They are typically viewed as a black-box,
and their internal structure is not specified, let alone used as a resource. In
this work, we demonstrate a low-loss waveguide circulator constructed with
single-crystalline yttrium iron garnet (YIG) in a 3D cavity, and analyze it as
a multi-mode hybrid quantum system with coupled photonic and magnonic
excitations. We show the coherent coupling of its chiral internal modes with
integrated superconducting niobium cavities, and how this enables tunable
non-reciprocal interactions between the intra-cavity photons. We also probe
experimentally the effective non-Hermitian dynamics of this system and its
effective non-reciprocal eigenmodes. The device platform provides a test bed
for implementing non-reciprocal interactions in open-system circuit QED.",2106.11283v2
2021-08-02,Spin Wave Computing using pre-recorded magnetization patterns,"We propose a novel type of a spin wave computing device, based on a bilayer
structure which includes a bias layer, made from a hard magnetic material and a
propagation layer, made from a magnetic material with low damping, for example,
Yttrium Garnet (YiG) or Permalloy. The bias layer maintains a stable
pre-recorded magnetization pattern, generating a bias field with a desired
spatial dependence, which in turn sets the equilibrium magnetization inside the
propagation layer. When an external source applies an RF field or spinwave to
the propagation layer, excited spin waves scatter on the magnetization's
inhomogenuities, resulting in a complex interference behavior. One thus has the
ability to adjust spin wave propagation properties simply by altering the
magnetization in the bias layer. We demonstrate that the phenomenon can be
utilized to perform a variety of computational operations, including Fourier
Transform, Vector-Matrix multiplication and Grover search algorithm, with the
operational parameters exceeding conventional designs by orders of magnitude.",2108.00909v1
2021-12-03,Microwave Amplification in a PT -symmetric-like Cavity Magnomechanical System,"We propose a scheme that can generate tunable magnomechanically induced
amplification in a double-cavity parity-time-(PT -) symmetric-like
magnomechanical system under a strong control and weak probe field. The system
consists of a ferromagnetic-material yttrium iron garnet (YIG) sphere placed in
a passive microwave cavity which is connected with another active cavity. We
reveal that ideally induced amplification of the microwave probe signal may
reach the maximum value 1000000 when cavity-cavity, cavity-magnon and
magnomechanical coupling strengths are nonzero simultaneously. The phenomenon
might have potential applications in the field of quantum information
processing and quantum optical devices. Besides, we also find the phenomena of
slow-light propagation. In this case, group speed delay of the light can
achieve 0.000035s, which can enhance some nonlinear effect. Moreover, due to
the relatively flat dispersion curve, the proposal may be applied to sensitive
optical switches, which plays an important role in storing photons and quantum
optical chips.",2112.01727v1
2021-12-07,Coupling function from bath density of states,"Modelling of an open quantum system requires knowledge of parameters that
specify how it couples to its environment. However, beyond relaxation rates,
realistic parameters for specific environments and materials are rarely known.
Here we present a method of inferring the coupling between a generic system and
its bosonic (e.g., phononic) environment from the experimentally measurable
density of states (DOS). With it we confirm that the DOS of the well-known
Debye model for three-dimensional solids is physically equivalent to choosing
an Ohmic bath. We further match a real phonon DOS to a series of Lorentzian
coupling functions, allowing us to determine coupling parameters for gold,
yttrium iron garnet (YIG) and iron as examples. The results illustrate how to
obtain material-specific dynamical properties, such as memory kernels. The
proposed method opens the door to more accurate modelling of relaxation
dynamics, for example for phonon-dominated spin damping in magnetic materials.",2112.04001v2
2021-12-08,Role of Magnon-Magnon Scattering in Magnon Polaron Spin Seebeck Effect,"The spin Seebeck effect (SSE) signal of magnon polarons in bulk-Y3Fe5O12
(YIG)/Pt heterostructures is found to drastically change as a function of
temperature. It appears as a dip in the total SSE signal at low temperatures,
but as the temperature increases, the dip gradually decreases before turning to
a peak. We attribute the observed dip-to-peak transition to the rapid rise of
the four-magnon scattering rate. Our analysis provides important insights into
the microscopic origin of the hybridized excitations and the overall
temperature dependence of the SSE anomalies.",2112.04621v1
2021-12-27,Observation of magnon cross-Kerr effect in cavity magnonics,"When there is a certain amount of field inhomogeneity, the biased
ferrimagnetic crystal will exhibit the higher-order magnetostatic (HMS) mode in
addition to the uniform-precession Kittel mode. In cavity magnonics, we show
both experimentally and theoretically the cross-Kerr-type interaction between
the Kittel mode and HMS mode. When the Kittel mode is driven to generate a
certain number of excitations, the HMS mode displays a corresponding frequency
shift and vice versa. The cross-Kerr effect is caused by an exchange
interaction between these two spin-wave modes. Utilizing the cross-Kerr effect,
we realize and integrate a multi-mode cavity magnonic system with only one
yttrium iron garnet (YIG) sphere. Our results will bring new methods to
magnetization dynamics studies and pave a way for novel cavity magnonic devices
by including the magnetostatic mode-mode interaction as an operational degree
of freedom.",2112.13807v1
2022-01-11,Edge spin wave transmission through a vertex domain wall in triangular dots,"Spin waves (SWs), being usually reflected by domain walls, could also be
channeled along them. Edge domain walls yield the interesting, and potentially
applicable to real devices property of broadband spin waves confinement to the
edges of the structure. Here we investigate through numerical simulations the
propagation of quasi one-dimensional spin waves in triangle-shaped amorphous
YIG ($Y_3Fe_5O_{12}$) micron sized ferromagnets as a function of the angle
aperture. The edge spin waves (ESWs) have been propagated over the corner in
triangles of 2 microns side with a fixed thickness of 85 nm. Parameters such as
superior vertex angle (in the range of 40$^\circ$-75$^\circ$) and applied
magnetic field have been optimized in order to obtain a higher transmission
coefficient of the ESWs over the triangle vertex. We observed that for a
certain aperture angle for which dominated ESW frequency coincides with one of
the localised DW modes, the transmission is maximized near one and the phase
shift drops to $\pi/2$ indicating resonant transmission of ESWs through the
upper corner. We compare the obtained results with existing theoretical models.
These results could contribute to the development of novel basic elements for
spin wave computing.",2201.04054v2
2022-01-11,Building instructions for a ferromagnetic axion haloscope,"A ferromagnetic haloscope is a rf spin-magnetometer used for searching Dark
Matter in the form of axions. A magnetic material is monitored searching for
anomalous magnetization oscillations which can be induced by dark matter
axions. To properly devise such instrument one first needs to understand the
features of the searched-for signal, namely the effective rf field of dark
matter axions $B_a$ acting on electronic spins. Once the properties of $B_a$
are defined, the design and test of the apparatus may start. The optimal sample
is a narrow linewidth and high spin-density material such as Yttrium Iron
Garnet (YIG), coupled to a microwave cavity with almost matched linewidth to
collect the signal. The power in the resonator is collected with an antenna and
amplified with a Josephson Parametric amplifier, a quantum-limited device
which, however, adds most of the setup noise. The signal is further amplified
with low noise HEMT and down-converted for storage with an heterodyne receiver.
This work describes how to build such apparatus, with all the experimental
details, the main issues one might face, and some solutions.",2201.04081v1
2022-02-06,Coexistence of coupling-induced transparency and absorption of transmission signals in magnon-mediated photon-photon coupling,"Coexistence of coupling-induced transparency (CIT) and absorption (CIA) of
signals in magnon-mediated photon-photon coupling was experimentally determined
in a planar hybrid structure consisting of a yttrium iron garnet (YIG) film and
three concentric inverted-split-ring resonators (ISRRs). The experimental
observation of simultaneous CIT and CIA phenomena was ascribed to
magnon-mediated photon-photon coupling between the individually decoupled
ISRRs. In order to capture the generic physics of the observed interactions, we
constructed an appropriate analytical model based on the balance between the
coherent and dissipative multiple-paths interactions, which model precisely
reproduced both the CIT and CIA experimentally observed from a single hybrid
system. This work, promisingly, can provide guidance for design of efficient,
flexible, and well-controllable photon-magnonic devices that are highly in
demand for applications to quantum technologies currently under development.",2202.02667v1
2022-02-07,Magnetization dynamics affected by phonon pumping,"""Pumping"" of phonons by a dynamic magnetization promises to extend the range
and functionality of magnonic devices. We explore the impact of phonon pumping
on room-temperature ferromagnetic resonance (FMR) spectra of bilayers of thin
yttrium iron garnet (YIG) films on thick gadolinium gallium garnet substrates
over a wide frequency range. At low frequencies the Kittel mode hybridizes
coherently with standing ultrasound waves of a bulk acoustic resonator to form
magnon polarons that induce rapid oscillations of the magnetic susceptibility,
as reported before. At higher frequencies, the phonon resonances overlap,
merging into a conventional FMR line, but with an increased line width. The
frequency dependence of the increased line broadening follows the predictions
from phonon pumping theory in the thick substrate limit. In addition, we find
substantial magnon-phonon coupling of a perpendicular standing spin wave (PSSW)
mode. This evidences the importance of the mode overlap between the acoustic
and magnetic modes, and provides a route towards engineering the magnetoelastic
mode coupling.",2202.03331v1
2022-03-30,Hybrid magnonics for short-wavelength spin waves facilitated by a magnetic heterostructure,"Recent research on hybrid magnonics has been restricted by the long magnon
wavelengths of the ferromagnetic resonance modes. We present an experiment on
the hybridization of 250-nm wavelength magnons with microwave photons in a
multimode magnonic system consists of a planar cavity and a magnetic bilayer.
The coupling between magnon modes in the two magnetic layers, i.e., the uniform
mode in Permalloy (Py) and the perpendicular standing spin waves (PSSWs) in
YIG, serves as an effective means for exciting short-wavelength PSSWs, which is
further hybridized with the photon mode of the microwave resonator. The
demonstrated magnon-photon coupling approaches the superstrong coupling regime,
and can even be achieved near zero bias field.",2203.16310v1
2022-04-14,Micro magnet location using spin waves,"In this work, we present experimental data demonstrating the feasibility of
magnetic object location using spin waves. The test structure includes a
Y$_3$Fe$_2$(FeO$_4$)$_3$) (YIG) film with four micro-antennas placed on the
edges. A constant in-plane bias magnetic field is provided by NdFeB permanent
magnet. Two antennas are used for spin wave excitation while the other two are
used for the inductive voltage measurement. There are nine selected places for
the magnet on the film. The magnet was subsequently placed in all nine
positions and spin wave transmission and reflection were measured. The obtained
experimental data show the difference in the output signal amplitude depending
on the magnet position. All nine locations can be identified by the frequency
and the amplitude of the absolute minimum in the output power. All experiments
are accomplished at room temperature. Potentially, spin waves can be utilized
for remote magnetic bit read-out. The disadvantages and physical constraints of
this approach are also discussed.",2204.07238v1
2022-06-02,Bistability in dissipatively coupled cavity magnonics,"Dissipative coupling of resonators arising from their cooperative dampings to
a common reservoir induces intriguingly new physics such as energy level
attraction. In this study, we report the nonlinear properties in a
dissipatively coupled cavity magnonic system. A magnetic material YIG (yttrium
iron garnet) is placed at the magnetic field node of a Fabry-Perot-like
microwave cavity such that the magnons and cavity photons are dissipatively
coupled. Under high power excitation, a nonlinear effect is observed in the
transmission spectra, showing bistable behaviors. The observed bistabilities
are manifested as clockwise, counterclockwise, and butterfly-like hysteresis
loops with different frequency detuning. The experimental results are well
explained as a Duffing oscillator dissipatively coupled with a harmonic one and
the required trigger condition for bistability could be determined
quantitatively by the coupled oscillator model. Our results demonstrate that
the magnon damping has been suppressed by the dissipative interaction, which
thereby reduces the threshold for conventional magnon Kerr bistability. This
work sheds light upon potential applications in developing low power
nonlinearity devices, enhanced anharmonicity sensors and for exploring the
non-Hermitian physics of cavity magnonics in the nonlinear regime.",2206.01231v1
2022-06-26,Tripartite high-dimensional magnon-photon entanglement in PT -symmetry broken phases of a non-Hermitian hybrid system,"Hybrid systems that combine spin ensembles and superconducting circuits
provide a promising platform for implementing quantum information processing.
We propose a non-Hermitian magnoncircuit-QED hybrid model consisting of two
cavities and an yttrium iron garnet (YIG) sphere placed in one of the cavities.
Abundant exceptional points (EPs), parity-time (PT )-symmetry phases and PT
-symmetry broken phases are investigated in the parameter space. Tripartite
highdimensional entangled states can be generated steadily among modes of the
magnon and photons in PT -symmetry broken phases, corresponding to which the
stable quantum coherence exists. Results show that the tripartite
high-dimensional entangled state is robust against the dissipation of hybrid
system, independent of a certain initial state, and insensitive to the
fluctuation of magnonphoton coupling. Further, we propose to simulate the
hybrid model with an equivalent LCR circuit. This work may provide prospects
for realizing multipartite high-dimensional entangled states in the
magnon-circuit-QED hybrid system.",2206.12769v1
2022-06-29,Mechanical Bistability in Kerr-modified Cavity Magnomechanics,"Bistable mechanical vibration is observed in a cavity magnomechanical system,
which consists of a microwave cavity mode, a magnon mode, and a mechanical
vibration mode of a ferrimagnetic yttrium-iron-garnet (YIG) sphere. The
bistability manifests itself in both the mechanical frequency and linewidth
under a strong microwave drive field, which simultaneously activates three
different kinds of nonlinearities, namely, magnetostriction, magnon self-Kerr,
and magnon-phonon cross-Kerr nonlinearities. The magnon-phonon cross-Kerr
nonlinearity is first predicted and measured in magnomechanics. The system
enters a regime where Kerr-type nonlinearities strongly modify the conventional
cavity magnomechanics that possesses only a radiation-pressure-like
magnomechanical coupling. Three different kinds of nonlinearities are
identified and distinguished in the experiment. Our work demonstrates a new
mechanism for achieving mechanical bistability by combining magnetostriction
and Kerr-type nonlinearities, and indicates that such Kerr-modified cavity
magnomechanics provides a unique platform for studying many distinct
nonlinearities in a single experiment.",2206.14588v2
2022-06-30,Second order nonlinearity induced multipartite entanglement in a hybrid magnon cavity QED system,"We present a proposal to produce bipartite and tripartite entanglement in a
hybrid magnon-cavity QED system. Two macroscopic yttrium iron garnet (YIG)
spheres are coupled to a single-mode microwave cavity via magnetic dipole
interaction, while the cavity photons are generated via the two photon process
induced by a pump field. Using the mean field theory, we show that the second
order nonlinearity can result in strong bipartite entanglement between cavity
photons and magnonic modes under two conditions, i.e., $\delta_c
\delta_{m}=2g^2$ and $\delta_c=-\delta_{m}$. For the later one, we also show
the possibility for producing the bipartite entanglement between two magnonic
modes and tripartite entanglement among the cavity photons and two magnonic
modes. Combining these two conditions, we further derive a third condition,
i.e., $\delta_m^2-\phi^2+2g^2=0$, where the tripartite entanglement can be
achieved when two magnonic modes have different resonant frequencies.",2206.15326v1
2022-08-02,Finite-frequency spin conductance of a ferro-/ferrimagnetic-insulator|normal-metal interface,"The interface between a ferro-/ferrimagnetic insulator and a normal metal can
support spin currents polarized collinear with and perpendicular to the
magnetization direction. The flow of angular momentum perpendicular to the
magnetization direction (""transverse"" spin current) takes place via spin torque
and spin pumping. The flow of angular momentum collinear with the magnetization
(""longitudinal"" spin current) requires the excitation of magnons. In this
article we extend the existing theory of longitudinal spin transport [Bender
and Tserkovnyak, Phys. Rev. B 91, 140402(R) (2015)] in the zero-frequency
weak-coupling limit in two directions: We calculate the longitudinal spin
conductance non-perturbatively (but in the low-frequency limit) and at finite
frequency (but in the limit of low interface transparency). For the
paradigmatic spintronic material system YIG|Pt, we find that non-perturbative
effects lead to a longitudinal spin conductance that is ca. 40% smaller than
the perturbative limit, whereas finite-frequency corrections are relevant at
low temperatures < 100 K only, when only few magnon modes are thermally
occupied.",2208.01420v1
2022-09-19,Cavity-mediated superconductor$\unicode{x2013}$ferromagnetic insulator coupling,"A recent proof of concept showed that cavity photons can mediate
superconducting (SC) signatures to a ferromagnetic insulator (FI) over a
macroscopic distance [Phys. Rev. B, 102, 180506(R) (2020)]. In contrast with
conventional proximity systems, this facilitates long-distance
FI$\unicode{x2013}$SC coupling, local subjection to different drives and
temperatures, and studies of their mutual interactions without proximal
disruption of their orders. Here we derive a microscopic theory for these
interactions, with an emphasis on the leading effect on the FI, namely, an
induced anisotropy field. In an arbitrary practical example, we find an
anisotropy field of $14 \unicode{x2013} 16$ $\mu$T, which is expected to yield
an experimentally appreciable tilt of the FI spins for low-coercivity FIs such
as Bi-YIG. We discuss the implications and potential applications of such a
system in the context of superconducting spintronics.",2209.09308v2
2022-11-10,High wave vector non-reciprocal spin wave beams,"We report unidirectional transmission of micron-wide spin waves beams in a 55
nm thin YIG. We downscaled a chiral coupling technique implementing Ni80Fe20
nanowires arrays with different widths and lattice spacing to study the
non-reciprocal transmission of exchange spin waves down to lambda = 80 nm. A
full spin wave spectroscopy analysis of these high wavevector coupled-modes
shows some difficulties to characterize their propagation properties, due to
both the non-monotonous field dependence of the coupling efficiency, and also
the inhomogeneous stray field from the nanowires.",2211.05514v2
2023-02-17,Entangling ferrimagnetic magnons with an atomic ensemble via opto-magnomechanics,"We show how to prepare macroscopic entanglement between an atomic ensemble
and a large number of magnons in a ferrimagnetic YIG crystal. Specifically, we
adopt an opto-magnomechanical configuration where the magnetostriction-induced
magnomechanical displacement couples to an optical cavity via radiation
pressure, and the latter further couples to an ensemble of two-level atoms that
are placed inside the cavity. We show that by properly driving the cavity and
magnon modes, optomechanical entanglement is created which is further
distributed to the atomic and magnonic systems, yielding stationary
entanglement between atoms and magnons. The atom-magnon entanglement is a
result of the combined effect of opto- and magnomechanical cooling and
optomechanical parametric down-conversion interactions. A competition mechanism
between two mechanical cooling channels is revealed. We further show that
genuine tripartite entanglement of three massive subsystems, i.e., atoms,
magnons and phonons, can also be achieved in the same system. Our results
indicate that the hybrid opto-magnomechanical system may become a promising
system for preparing macroscopic quantum states involving magnons, photons,
phonons and atoms.",2302.08684v2
2023-02-21,Aluminium substituted yttrium iron garnet thin films with reduced Curie temperature,"Magnetic garnets such as yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$, YIG) are
widely used in spintronic and magnonic devices. Their magnetic and
magneto-optical properties can be modified over a wide range by tailoring their
chemical composition. Here, we report the successful growth of Al-substituted
yttrium iron garnet (YAlIG) thin films via radio frequency sputtering in
combination with an ex situ annealing step. Upon selecting appropriate process
parameters, we obtain highly crystalline YAlIG films with different Al$^{3+}$
substitution levels on both, single crystalline Y$_3$Al$_5$O$_{12}$ (YAG) and
Gd$_3$Ga$_5$O$_{12}$ (GGG) substrates. With increasing Al$^{3+}$ substitution
levels, we observe a reduction of the saturation magnetisation as well as a
systematic decrease of the magnetic ordering temperature to values well below
room temperature. YAlIG thin films thus provide an interesting material
platform for spintronic and magnonic experiments in different magnetic phases.",2302.10517v2
2023-03-20,Secondary Excitation of Spin-Waves: How Electromagnetic Cross-Talk Impacts on Magnonic Devices,"This work examines the impact of electromagnetic cross-talk in magnonic
devices when using inductive spin-wave (SW) transducers. We present detailed
electrical SW spectroscopy measurements showing the signal contributions to be
considered in magnonic device design. We further provide a rule of thumb
estimation for the cross-talk that is responsible for the secondary SW
excitation at the output transducer. Simulations and calibrated electrical
characterizations underpin this method. Additionally, we visualize the
secondary SW excitation via time-resolved MOKE imaging in the forward-volume
configuration in a 100nm Yttrium-Iron-Garnet (YIG) system. Our work is a step
towards fast yet robust joint electromagentic-micromagnetic magnonic device
design.",2303.11303v2
2023-03-26,Compact localised states in magnonic Lieb lattices,"Lieb lattice is one of the simplest bipartite lattices where compact
localized states (CLS) are observed. This type of localisation is induced by
the peculiar topology of the unit cell, where the modes are localized only on
one sublattice due to the destructive interference of partial waves. The CLS
exist in the absence of defects and are associated with the flat bands in the
dispersion relation. The Lieb lattices were successfully implemented as optical
lattices or photonic crystals. This work demonstrates the possibility of
magnonic Lieb lattice realization where the flat bands and CLS can be observed
in the planar structure of sub-micron in-plane sizes. Using forward volume
configuration, we investigated numerically (using the finite element method)
the Ga-dopped YIG layer with cylindrical inclusions (without Ga content)
arranged in a Lieb lattice of the period 250 nm. We tailored the structure to
observe, for the few lowest magnonic bands, the oscillatory and evanescent spin
waves in inclusions and matrix, respectively. Such a design reproduces the Lieb
lattice of nodes (inclusions) coupled to each other by the matrix with the CLS
in flat bands.",2303.14843v1
2023-03-27,Temperature dependent study of the spin dynamics of coupled Y$_3$Fe$_5$O$_{12}$/Gd$_3$Fe$_5$O$_{12}$/Pt trilayers,"In this study, we investigate the dynamic response of a Y$_3$Fe$_5$O$_{12}$
(YIG)/ Gd$_3$Fe$_5$O$_{12}$ (GdIG)/ Pt trilayer system by measurements of the
ferromagnetic resonance (FMR) and the pumped spin current detected by the
inverse spin Hall effect. This trilayer system offers the unique opportunity to
investigate the spin dynamics of the ferrimagnetic GdIG, close to its
compensation temperature. We show that our trilayer acts as a highly tunable
spin current source. Our experimental results are supported by micro-magnetic
simulations. As the detected spin current in the top Pt layer is distinctly
dominated by the GdIG layer, this gives the unique opportunity to investigate
the excitation and dynamic properties of GdIG while comparing it to the
broadband FMR absorption spectrum of the heterostructure.",2303.15085v1
2023-04-04,Full quantum theory for magnon transport in two-sublattice magnetic insulators and magnon junctions,"Magnon, as elementary excitation in magnetic systems, can carry and transfer
angular momentum. Due to the absence of Joule heat during magnon transport,
researches on magnon transport have gained considerable interests over the past
decade. Recently, a full quantum theory has been employed to investigate magnon
transport in ferromagnetic insulators (FMIs). However, the most commonly used
magnetic insulating material in experiments, yttrium iron garnet (YIG), is a
ferrimagnetic insulator (FIMI). Therefore, a full quantum theory for magnon
transport in FIMI needs to be established. Here, we propose a Green's function
formalism to compute the magnon bulk and interface current in both FIMIs and
antiferromagnetic insulators (AFMIs). We investigate the spatial distribution
and temperature dependence of magnon current in FIMIs and AFMIs generated by
temperature or spin chemical potential step. In AFMIs, magnon currents
generated by temperature step in the two sublattices cancel each other out.
Subsequently, we numerically simulate the magnon junction effect using the
Green's function formalism, and result shows near 100\% magnon junction ratio.
This study demonstrates the potential for investigating magnon transport in
specific magnonic devices using a full quantum theory.",2304.01930v1
2023-04-19,Nonreciprocal ultrastrong magnon-photon coupling in the bandgap of photonic crystals,"We observe a nonreciprocal ultrastrong magnon-photon coupling in the bandgap
of photonic crystals by introducing a single crystal YIG cylinder into copper
photonic crystals cavity as a point defect. The coupling strength reaches up to
1.18 GHz, which constitutes about 10.9% of the photon energy compared to the
photon frequency around 10.8 GHz. It is fascinating that the coupling achieves
unidirectional signal transmission in the whole bandgap. This study
demonstrates the possibility of controlling nonreciprocal magnon-photon
coupling by manipulating the structure of photonic crystals, providing new
methods to investigate the influence of magnetic point defects on microwave
signal transmission.",2304.09627v1
2023-04-26,Critical Cavity-Magnon Polariton Mediated Strong Long-Distance Spin-Spin Coupling,"Strong long-distance spin-spin coupling is desperately demanded for
solid-state quantum information processing, but it is still challenged. Here,
we propose a hybrid quantum system, consisting of a coplanar waveguide (CPW)
resonator weakly coupled to a single nitrogen-vacancy spin in diamond and a
yttrium-iron-garnet (YIG) nanosphere holding Kerr magnons, to realize strong
long-distance spin-spin coupling. With a strong driving field on magnons, the
Kerr effect can squeeze magnons, and thus exponentially enhance the coupling
between the CPW resonator and the squeezed magnons, which produces two
cavity-magnon polaritons, i.e., the high-frequency polariton (HP) and
low-frequency polariton (LP). When the enhanced cavity-magnon coupling
approaches to the critical value, the spin is fully decoupled from the HP,
while the coupling between the spin and the LP is significantly improved. In
the dispersive regime, a strong spin-spin coupling is achieved with accessible
parameters, and the coupling distance can be up to $\sim$cm. Our proposal
provides a promising way to manipulate remote solid spins and perform quantum
information processing in weakly coupled hybrid systems.",2304.13553v2
2023-05-10,Proposal for optomagnonic teleportation and entanglement swapping,"A protocol for realizing discrete-variable quantum teleportation in an
optomagnonic system is provided. Using optical pulses, an arbitrary photonic
qubit state encoded in orthogonal polarizations is transferred onto the joint
state of a pair of magnonic oscillators in two macroscopic yttrium-iron-garnet
(YIG) spheres that are placed in an optical interferometer. We further show
that optomagnonic entanglement swapping can be realized in an extended
dual-interferometer configuration with a joint Bell-state detection.
Consequently, magnon Bell states are prepared. We analyze the effect of the
residual thermal occupation of the magnon modes on the fidelity in both the
teleportation and entanglement swapping protocols.",2305.05889v1
2023-05-19,Quantum transduction of superconducting qubit in electro-optomechanical and electro-optomagnonical system,"We study the quantum transduction of a superconducting qubit to an optical
photon in electro-optomechanical and electro-optomagnonical systems. The
electro-optomechanical system comprises a flux-tunable transmon qubit coupled
to a suspended mechanical beam, which then couples to an optical cavity.
Similarly, in an electro-optomagnonical system, a flux-tunable transmon qubit
is coupled to an optical whispering gallery mode via a magnon excitation in a
YIG ferromagnetic sphere. In both systems, the transduction process is done in
sequence. In the first sequence, the qubit states are encoded in coherent
excitations of phonon/magnon modes through the phonon/magnon-qubit interaction,
which is non-demolition in the qubit part. We then measure the phonon/magnon
excitations, which reveal the qubit states, by counting the average number of
photons in the optical cavities. The measurement of the phonon/magnon
excitations can be performed at a regular intervals of time.",2305.11629v1
2023-07-18,Distant entanglement via photon hopping in a coupled magnomechanical system,"We theoretically propose a scheme to generate distant bipartite entanglement
between various subsystems in coupled magnomechanical systems where both the
microwave cavities are coupled through single photon hopping parameter. Each
cavity also contains a magnon mode and phonon mode and this gives five
excitation modes in our model Hamiltonian which are cavity-1 photons, cavity-2
photons, magnon, and phonon modes in both YIG spheres. We found that
significant bipartite entanglement exists between indirectly coupled subsystems
in coupled microwave cavities for an appropriate set of parameters regime.
Moreover, we also obtain suitable cavity and magnon detuning parameters for a
significant distant bipartite entanglement in different bipartitions. In
addition, it can be seen that a single photon hopping parameter significantly
affects both the degree as well as the transfer of quantum entanglement between
various bipartitions. Hence, our present study related to coupled microwave
cavity magnomechanical configuration will open new perspectives in coherent
control of various quantum correlations including quantum state transfer among
macroscopic quantum systems",2307.09424v1
2023-07-19,Enhanced bipartite entanglement and Gaussian quantum steering of squeezed magnon modes,"We theoretically investigate a scheme to entangle two squeezed magnon modes
in a double cavitymagnon system, where both cavities are driven by a two-mode
squeezed vacuum microwave field. Each cavity contains an optical parametric
amplifier as well as a macroscopic yttrium iron garnet (YIG) sphere placed near
the maximum bias magnetic fields such that this leads to the excitation of the
relevant magnon mode and its coupling with the corresponding cavity mode. We
have obtained optimal parameter regimes for achieving the strong magnon-magnon
entanglement and also studied the effectiveness of this scheme towards the
mismatch of both the cavity-magnon couplings and decay parameters. We have also
explored the entanglement transfer efficiency including Gaussian quantum
steering in our proposed system",2307.09846v1
2023-08-11,Kerr nonlinearity induced strong spin-magnon coupling,"One pillar of quantum magnonics is the exploration of the utilization of the
mediation role of magnons in different platforms to develop quantum
technologies. The efficient coupling between magnons and various quantum
entities is a prerequisite. Here, we propose a scheme to enhance the
spin-magnon coupling by the magnonic Kerr nonlinearity in a YIG sphere. We find
that the Kerr-enhanced spin-magnon coupling invalidates the widely used
single-Kittel-mode approximation to magnons. It is revealed that the spin
decoherence induced by the multimode magnons in the strong-coupling regime
becomes not severe, but suppressed, manifesting as either population trapping
or persistent Rabi-like oscillation. This anomalous effect is because the spin
changes to be so hybridized with the magnons that one or two bound states are
formed between them. Enriching the spin-magnon coupling physics, the result
supplies a guideline to control the spin-magnon interface.",2308.05927v2
2023-08-15,Global biasing using a Hardware-based artificial Zeeman term in Spinwave Ising Machines,"A spinwave Ising machine (SWIM) is a newly proposed type of time-multiplexed
hardware solver for combinatorial optimization that employs feedback coupling
and phase sensitive amplification to map an Ising Hamiltonian into
phase-binarized propagating spin-wave RF pulses in an Yttrium-Iron-Garnet (YIG)
film. In this work, we increase the mathematical complexity of the SWIM by
adding a global Zeeman term to a 4-spin MAX-CUT Hamiltonian using a continuous
external electrical signal with the same frequency as the spin pulses and phase
locked with with one of the two possible states. We are able to induce
ferromagnetic ordering in both directions of the spin states despite
antiferromagnetic pairwise coupling. Embedding a planar antiferromagnetic spin
system in a magnetic field has been proven to increase the complexity of the
graph associated to its Hamiltonian and thus this straightforward
implementation helps explore higher degrees of complexity in this evolving
solver.",2308.07718v1
2023-08-28,Spin wave mode conversion in an in-plane magnetized microscale T-shaped YIG magnonic splitter,"As one of the fundamental magnonic devices, a magnonic splitter device has
been proposed and spin wave propagation in this device has been studied
numerically and experimentally. In the present work, we fabricated a T-shaped
magnonic splitter with 6 $\mu$m-wide three arms using a 100 nm-thick yttrium
iron garnet film and, using time-resolved magneto-optic Kerr microscopy,
observed that spin waves split into both, the vertical and the horizontal
direction at the junction. Analyzing the results, we found that spin wave modes
are converted into another during the splitting process and the splitting
efficiency is dominantly dependent on the 1st order of incoming spin waves.",2308.14327v1
2023-09-28,Engineering Entangled Coherent States of Magnons and Phonons via a Transmon Qubit,"We propose a scheme for generating and controlling entangled coherent states
(ECS) of magnons, i.e. the quanta of the collective spin excitations in
magnetic systems, or phonons in mechanical resonators. The proposed hybrid
circuit architecture comprises a superconducting transmon qubit coupled to a
pair of magnonic Yttrium Iron Garnet (YIG) spherical resonators or mechanical
beam resonators via flux-mediated interactions. Specifically, the coupling
results from the magnetic/mechanical quantum fluctuations modulating the qubit
inductor, formed by a superconducting quantum interference device (SQUID). We
show that the resulting radiation-pressure interaction of the qubit with each
mode, can be employed to generate maximally-entangled states of magnons or
phonons. In addition, we numerically demonstrate a protocol for the preparation
of magnonic and mechanical Bell states with high fidelity including realistic
dissipation mechanisms. Furthermore, we have devised a scheme for reading out
the prepared states using standard qubit control and resonator field
displacements. Our work demonstrates an alternative platform for quantum
information using ECS in hybrid magnonic and mechanical quantum networks.",2309.16514v1
2023-10-09,Bath-induced spin inertia,"Spin dynamics is usually described as massless or, more precisely, as free of
inertia. Recent experiments, however, found direct evidence for inertial spin
dynamics. In turn, it is necessary to rethink the basics of spin dynamics.
Focusing on a macrospin in an environment (bath), we show that the spin-to-bath
coupling gives rise to spin inertia. This bath-induced spin inertia appears
universally from all the high-frequency bath modes. We expect our results to
provide new insights into recent experiments on spin inertia. Moreover, they
indicate that any channel for spin dissipation should also be accompanied by a
term accounting for bath-induced spin inertia. As an illustrative example, we
consider phonon-bath-induced spin inertia in a YIG/GGG stack.",2310.05621v2
2023-11-30,Nanoscaled magnon transistor based on stimulated three-magnon splitting,"Magnonics is a rapidly growing field, attracting much attention for its
potential applications in data transport and processing. Many individual
magnonic devices have been proposed and realized in laboratories. However, an
integrated magnonic circuit with several separate magnonic elements has yet not
been reported due to the lack of a magnonic amplifier to compensate for
transport and processing losses. The magnon transistor reported in [Nat.
Commun. 5, 4700, (2014)] could only achieve a gain of 1.8, which is
insufficient in many practical cases. Here, we use the stimulated three-magnon
splitting phenomenon to numerically propose a concept of magnon transistor in
which the energy of the gate magnons at 14.6 GHz is directly pumped into the
energy of the source magnons at 4.2 GHz, thus achieving the gain of 9. The
structure is based on the 100 nm wide YIG nano-waveguides, a directional
coupler is used to mix the source and gate magnons, and a dual-band magnonic
crystal is used to filter out the gate and idler magnons at 10.4 GHz frequency.
The magnon transistor preserves the phase of the signal and the design allows
integration into a magnon circuit.",2311.18479v1
2023-12-14,Magnetization Reversal of 50-nm-wide Ni81Fe19 Nanostripes by Ultrashort Magnons in Yttrium Iron Garnet for Memory-Enhanced Magnonic Circuits,"Spin waves (magnons) can enable wave-based neuromorphic computing by which
one aims at overcoming limitations inherent to conventional electronics and the
von Neumann architecture. In this study, we explore the storage of magnon
signals and the magnetization switching of periodic and aperiodic arrays of
Ni81Fe19 (Py) nanostripes with widths (w) between 50 nm and 200 nm. Spin waves
excited with low microwave power in yttrium iron garnet induce the reversal of
the nanostripes of different w in a small opposing field. Exploiting
microwave-to-magnon transducers for magnon modes with ultrashort wavelengths,
we demonstrate the reversal of 50-nm-wide Py nanostripes by magnons with
wavelength ~ 100 nm after they have propagated over 25 micrometer in YIG. The
findings are important for designing a magnon-based in-memory computing device.",2312.09177v1
2023-12-17,An Edge-Coupled Magnetostatic Bandpass Filter,"This paper reports on the design, fabrication, and characterization of an
edge-coupled magnetostatic forward volume wave bandpass filter. Using
micromachining techniques, the filter is fabricated from a yttrium iron garnet
(YIG) film grown on a gadolinium gallium garnet (GGG) substrate with inductive
transducers. By adjusting an out-of-plane magnetic field, we demonstrate linear
center frequency tuning for a $4^{\text{th}}$-order filter from 4.5 GHz to 10.1
GHz while retaining a fractional bandwidth of 0.3%, an insertion loss of 6.94
dB, and a -35dB rejection. We characterize the filter nonlinearity in the
passband and stopband with IIP3 measurements of -4.85 dBm and 25.84 dBm,
respectively. When integrated with a tunable magnetic field, this device is an
octave tunable narrowband channel-select filter.",2312.10583v1
2023-12-20,Non-equilibrium criticality at the onset of time-crystalline order in $O(N)$ models,"We explore the phase transitions at the onset of time-crystalline order in
$O(N)$ models driven out-of-equilibrium. The spontaneous breaking of time
translation symmetry and its Goldstone mode are captured by an effective
description with $O(N)\times SO(2)$ symmetry. Using the renormalization group
and the $\epsilon=4-d$ expansion in a leading two-loop analysis, we identify a
new non-equilibrium universality class. Strikingly, it controls the
long-distance physics no matter how small the microscopic breaking of
equilibrium conditions is. The $O(N=2)\times SO(2)$ symmetry group is realized
for magnon condensation in pumped yttirum iron garnet (YIG) films and in
exciton-polariton systems with a polarization degree of freedom.",2312.13372v1
2024-01-22,Theory of momentum-resolved magnon electron energy loss spectra: The case of Yttrium Iron Garnet,"We explore the inelastic spectra of electrons impinging in a magnetic system.
The methodology here presented is intended to highlight the charge-dependent
interaction of the electron beam in a STEM-EELS experiment, and the local
vector potential generated by the magnetic lattice. This interaction shows an
intensity $10^{-2}$ smaller than the purely spin interaction, which is taken to
be functionally the same as in the inelastic neutron experiment. On the other
hand, it shows a strong scattering vector dependence ($\kappa^{-4}$) and a
dependence with the relative orientation between the probe wavevector and the
local magnetic moments of the solid. We present YIG as a case study due to its
high interest by the community.",2401.12302v2
2024-01-30,Entropy production rate and correlations of cavity magnomechanical system,"We present the irreversibility generated by a stationary cavity
magnomechanical system composed of a yttrium iron garnet (YIG) sphere with a
diameter of a few hundred micrometers inside a microwave cavity. In this
system, the magnons, i.e., collective spin excitations in the sphere, are
coupled to the cavity photon mode via magnetic dipole interaction and to the
phonon mode via magnetostrictive force (optomechanical-like). We employ the
quantum phase space formulation of the entropy change to evaluate the
steady-state entropy production rate and associated quantum correlation in the
system. We find that the behavior of the entropy flow between the cavity photon
mode and the phonon mode is determined by the magnon-photon coupling and the
cavity photon dissipation rate. Interestingly, the entropy production rate can
increase/decrease depending on the strength of the magnon-photon coupling and
the detuning parameters. We further show that the amount of correlations
between the magnon and phonon modes is linked to the irreversibility generated
in the system for small magnon-photon coupling. Our results demonstrate the
possibility of exploring irreversibility in driven magnon-based hybrid quantum
systems and open a promising route for quantum thermal applications.",2401.16857v1
2024-02-07,Breaking surface plasmon excitation constraint via surface spin waves,"Surface plasmons in two-dimensional (2D) electron systems have attracted
great attention for their promising light-matter applications. However, the
excitation of a surface plasmon, in particular, transverse-electric (TE)
surface plasmon, remains an outstanding challenge due to the difficulty to
conserve energy and momentum simultaneously in the normal 2D materials. Here we
show that the TE surface plasmons ranging from gigahertz to terahertz regime
can be effectively excited and manipulated in a hybrid dielectric, 2D material
and magnet structure. The essential physics is that the surface spin wave
supplements an additional freedom of surface plasmon excitation and thus
greatly enhances the electric field in the 2D medium. Based on widely-used
magnetic materials like yttrium iron garnet (YIG) and manganese difluoride
($\mathrm{MnF}_2$), we further show that the plasmon excitation manifests
itself as a measurable dip in the reflection spectrum of the hybrid system
while the dip position and the dip depth can be well controlled by the electric
gating on the 2D layer and an external magnetic field. Our findings should
bridge the fields of low-dimensional physics, plasmonics and spintronics and
open a novel route to integrate plasmonic and spintronic devices.",2402.04626v1
2024-03-23,Spatial Control of Hybridization-Induced Spin-Wave Transmission Stop Band,"Spin-wave (SW) propagation close to the hybridization-induced transmission
stop band is investigated within a trapezoid-shaped 200\,nm thick yttrium iron
garnet (YIG) film using time-resolved magneto-optic Kerr effect (TR-MOKE)
microscopy and broadband spin wave spectroscopy, supported by micromagnetic
simulations. The gradual reduction of the effective field within the structure
leads to local variations of the SW dispersion relation and results in a SW
hybridization at a fixed position in the trapezoid where the propagation
vanishes since the SW group velocity approaches zero. By tuning external field
or frequency, spatial control of the spatial stop band position and spin-wave
propagation is demonstrated and utilized to gain transmission control over
several microstrip lines.",2403.15840v1
2001-04-30,Measurement of the Relativistic Potential Difference Across a Rotating Dielectric Cylinder,"According to the Special Theory of Relativity, a rotating magnetic dielectric
cylinder in an axial magnetic field should exhibit a contribution to the radial
electric potential that is associated with the motion of the material's
magnetic dipoles. In 1913 Wilson and Wilson reported a measurement of the
potential difference across a magnetic dielectric constructed from wax and
steel balls. Their measurement has long been regarded as a verification of this
prediction. In 1995 Pelligrini and Swift questioned the theoretical basis of
experiment. In particular, they pointed out that it is not obvious that a
rotating medium may be treated as if each point in the medium is locally
inertial. They calculated the effect in the rotating frame and predicted a
potential different from both Wilson's theory and experiment. Subsequent
analysis of the experiment suggests that Wilson's experiment does not
distinguish between the two predictions due to the fact that their composite
steel-wax cylinder is conductive in the regions of magnetization. We report
measurements of the radial voltage difference across various rotating
dielectric cylinders, including a homogeneous magnetic material (YIG), to
unambiguously test the competing calculations. Our results are compatible with
the traditional treatment of the effect using a co-moving locally inertial
reference frame, and are incompatible with the predictions based on the model
of Pelligrini and Swift.",0104101v1
2013-06-04,Determination of the origin of the spin Seebeck effect - bulk vs. interface effects,"The observation of the spin Seebeck effect in insulators has meant a
breakthrough for spin caloritronics due to the unique ability to generate pure
spin currents by thermal excitations in insulating systems without moving
charge carriers. Since the recent first observation, the underlying mechanism
and the origin of the observed signals have been discussed highly
controversially. Here we present a characteristic dependence of the
longitudinal spin Seebeck effect amplitude on the thickness of the insulating
ferromagnet (YIG). Our measurements show that the observed behavior cannot be
explained by any effects originating from the interface, such as magnetic
proximity effects in the spin detector (Pt). Comparison to theoretical
calculations of thermal magnonic spin currents yields qualitative agreement for
the thickness dependence resulting from the finite effective magnon propagation
length so that the origin of the effect can be traced to genuine bulk magnonic
spin currents ruling out parasitic interface effects.",1306.0784v1
2015-02-15,Redefinition of spin Hall magnetoresistance,"Using a multi-conduction-channel model, we redefined the micromechanism of
spin Hall magnetoresistance (SMR). Four conduction channels are created by spin
accumulation of nonpolarized electron flow at top, bottom, left and right
interfaces of the film sample, which corresponds to different resistance states
of polarized electron flow with various spin directions relative to the applied
magnetic field ($\mathbf{H}$), and brings about the SMR effect finally. The
magnetic insulator layer, such as yttrium iron garnet (YIG), is not a requisite
for the observation of SMR. Instead, the SMR effect is perfectly realized, with
an order of magnitude increase, in the sample with a discontinuous layer of
isolated-Co$_2$FeAl (0.3 nm) grains covered by 2.5-nm-thick Pt layer on MgO
substrate. The model intuitively gives the typical relationship of SMR effect,
i.e. $\rho_{\parallel}\approx\rho_{\bot}>\rho_{T}$, where $\rho_{\bot}$,
$\rho_{\parallel}$ and $\rho_{T}$ are longitudinal reisitivities with applied
magnetic field ($\mathbf{H}$) direction perpendicular to the current direction
out of plane (as Z direction), parallel with and perpendicular to it in plane
(as X and Y direction), respectively. Our research reveals that the scattering
between polarized and nonpolarized conduction electrons is the origin of SMR,
and the intrinsic SMR is not constant when $\mathbf{H}$ direction rotates in XZ
plane, which is distinct from that in the reported SMR mechanism.",1502.04288v1
2016-01-08,Magnons and Phonons Optically Driven Out of Local Equilibrium in a Magnetic Insulator,"Magnons are the energy quanta of fundamental spin excitations, namely spin
waves, and they can make a considerable contribution to energy transport in
some magnetic materials in a similar manner as lattice vibration waves or
phonons. The coupling and possible non-equilibrium between magnons and other
energy carriers have been used to explain several recently discovered thermally
driven spin transport and energy conversion phenomena. Here, we report
experiments in which local non-equilibrium between magnons and phonons in a
single crystalline bulk magnetic insulator, Y3Fe5O12 (yttrium iron garnet, or
YIG), has been created optically within a focused laser spot and probed
directly with the use of micro-Brillouin light scattering (BLS). By analyzing
the experimental results with a thermally induced magnon diffusion model, we
obtain the magnon diffusion length of thermal magnons. By explicitly
establishing non-equilibrium between magnons and phonons, our studies represent
an important step toward a quantitative understanding of various spin-heat
coupling phenomena.",1601.01982v3
2017-01-12,Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method,"The determination of the longitudinal spin Seebeck effect (LSSE) coefficient
is currently plagued by a large uncertainty due to the poor reproducibility of
the experimental conditions used in its measurement. In this work we present a
detailed analysis of two different methods used for the determination of the
LSSE coefficient. We have performed LSSE experiments in different laboratories,
by using different setups and employing both the temperature difference method
and the heat flux method. We found that the lack of reproducibility can be
mainly attributed to the thermal contact resistance between the sample and the
thermal baths which generate the temperature gradient. Due to the variation of
the thermal resistance, we found that the scaling of the LSSE voltage to the
heat flux through the sample rather than to the temperature difference across
the sample greatly reduces the uncertainty. The characteristics of a single
YIG/Pt LSSE device obtained with two different setups was $(1.143\pm0.007)\cdot
10^{-7}$ Vm/W and $(1.101\pm0.015)\cdot 10^{-7}$ Vm/W with the heat flux method
and $(2.313\pm0.017)\cdot 10^{-7}$ V/K and $(4.956\pm0.005)\cdot 10^{-7}$ V/K
with the temperature difference method. This shows that systematic errors can
be considerably reduced with the heat flux method.",1701.03285v3
2017-09-06,Complex THz and DC inverse spin Hall effect in YIG/Cu$_{1-x}$Ir$_{x}$ bilayers across a wide concentration range,"We measure the inverse spin Hall effect of Cu$_{1-x}$Ir$_{x}$ thin films on
yttrium iron garnet over a wide range of Ir concentrations ($0.05 \leqslant x
\leqslant 0.7$). Spin currents are triggered through the spin Seebeck effect,
either by a DC temperature gradient or by ultrafast optical heating of the
metal layer. The spin Hall current is detected by, respectively, electrical
contacts or measurement of the emitted THz radiation. With both approaches, we
reveal the same Ir concentration dependence that follows a novel complex,
non-monotonous behavior as compared to previous studies. For small Ir
concentrations a signal minimum is observed, while a pronounced maximum appears
near the equiatomic composition. We identify this behavior as originating from
the interplay of different spin Hall mechanisms as well as a
concentration-dependent variation of the integrated spin current density in
Cu$_{1-x}$Ir$_{x}$. The coinciding results obtained for DC and ultrafast
stimuli show that the studied material allows for efficient spin-to-charge
conversion even on ultrafast timescales, thus enabling a transfer of
established spintronic measurement schemes into the terahertz regime.",1709.01890v1
2018-10-05,Magnon contribution to unidirectional spin Hall magnetoresistance,"We develop a model for the magnonic contribution to the unidirectional spin
Hall magnetoresistance (USMR) of heavy metal/ferromagnetic insulator bilayer
films. We show that diffusive transport of Holstein-Primakoff magnons leads to
an accumulation of spin near the bilayer interface, giving rise to a
magnoresistance which is not invariant under inversion of the current
direction. Unlike the electronic contribution described by Zhang and Vignale
[Phys. Rev. B 94, 140411 (2016)], which requires an electrically conductive
ferromagnet, the magnonic contribution can occur in ferromagnetic insulators
such as yttrium iron garnet. We show that the magnonic USMR is, to leading
order, cubic in the spin Hall angle of the heavy metal, as opposed to the
linear relation found for the electronic contribution. We estimate that the
maximal magnonic USMR in Pt|YIG bilayers is on the order of $10^{-8}$, but may
reach values of up to $10^{-5}$ if the magnon gap is suppressed, and can thus
become comparable to the electronic contribution in, e.g., Pt|Co. We show that
the magnonic USMR at a finite magnon gap may be enhanced by an order of
magnitude if the magnon diffusion length is decreased to a specific optimal
value that depends on various system parameters.",1810.02610v2
2018-10-16,Spin-torque oscillation in a magnetic insulator probed by a single-spin sensor,"Coherent, self-sustained oscillation of magnetization in spin-torque
oscillators (STOs) is a promising source for on-chip, nanoscale generation of
microwave magnetic fields. Such fields could be used for local excitation of
spin-wave resonances, control of spin qubits, and studies of paramagnetic
resonance. However, local characterization of fields emitted by an STO has
remained an outstanding challenge. Here, we use the spin of a single
nitrogen-vacancy (NV) defect in diamond to probe the magnetic fields generated
by an STO in a microbar of ferromagnetic insulator yttrium-iron-garnet (YIG).
The combined spectral resolution and sensitivity of the NV sensor allows us to
resolve multiple spin-wave modes and characterize their damping. When damping
is decreased sufficiently via spin injection, the modes auto-oscillate, as
indicated by a strongly reduced linewidth, a diverging magnetic power spectral
density, and synchronization of the STO frequency to an external microwave
source. These results open the way for quantitative, nanoscale mapping of the
microwave signals generated by STOs, as well as harnessing STOs as local probes
of mesoscopic spin systems.",1810.07306v1
2018-11-02,Evidence for exchange Dirac gap in magneto-transport of topological insulator-magnetic insulator heterostructures,"Transport signatures of exchange gap opening because of magnetic proximity
effect (MPE) are reported for bilayer structures of Bi2Se3 thin films on
yttrium iron garnet (YIG) and thulium iron garnet (TmIG) of perpendicular
magnetic anisotropy (PMA). Pronounced negative magnetoresistance (MR) was
detected, and attributed to an emergent weak localization (WL) effect
superimposing on a weak antilocalization (WAL). Thickness-dependent study shows
that the WL originates from the time-reversal-symmetry breaking of topological
surface states by interfacial exchange coupling. The weight of WL declined when
the interfacial magnetization was aligned toward the in-plane direction, which
is understood as the effect of tuning the exchange gap size by varying the
perpendicular magnetization component. Importantly, magnetotransport study
revealed anomalous Hall effect (AHE) of square loops and anisotropic
magnetoresistance (AMR) characteristic, typifying a ferromagnetic conductor in
Bi2Se3/TmIG, and the presence of an interfacial ferromagnetism driven by MPE.
Coexistence of MPE-induced ferromagnetism and the finite exchange gap provides
an opportunity of realizing zero magnetic-field dissipation-less transport in
topological insulator/ferromagnetic insulator heterostructures.",1811.00689v1
2019-01-28,Spin Hall magnetoresistance in heterostructures consisting of noncrystalline paramagnetic YIG and Pt,"The spin Hall magnetoresistance (SMR) effect arises from spin-transfer
processes across the interface between a spin Hall active metal and an
insulating magnet. While the SMR response of ferrimagnetic and
antiferromagnetic insulators has been studied extensively, the SMR of a
paramagnetic spin ensemble is not well established. Thus, we investigate herein
the magnetoresistive response of as-deposited yttrium iron garnet/platinum thin
film bilayers as a function of the orientation and the amplitude of an
externally applied magnetic field. Structural and magnetic characterization
show no evidence for crystalline order or spontaneous magnetization in the
yttrium iron garnet layer. Nevertheless, we observe a clear magnetoresistance
response with a dependence on the magnetic field orientation characteristic for
the SMR. We propose two models for the origin of the SMR response in
paramagnetic insulator/Pt heterostructures. The first model describes the SMR
of an ensemble of non-interacting paramagnetic moments, while the second model
describes the magnetoresistance arising by considering the total net moment.
Interestingly, our experimental data are consistently described by the net
moment picture, in contrast to the situation in compensated ferrimagnets or
antiferromagnets.",1901.09986v1
2019-03-05,All-optical cryogenic thermometry based on NV centers in nanodiamonds,"The nitrogen-vacancy (NV) center in diamond has been recognized as a
high-sensitivity nanometer-scale metrology platform. Thermometry has been a
recent focus, with attention largely confined to room temperature applications.
Thermometry has been a recent focus, with attention largely confined to room
temperature applications. Temperature sensing at low temperatures, however,
remains challenging as the sensitivity decreases for many commonly used
techniques which rely on a temperature dependent frequency shift of the NV
centers spin resonance and its control with microwaves. Here we use an
alternative approach that does not require microwaves, ratiometric all-optical
thermometry, and demonstrate that it may be utilized to liquid nitrogen
temperatures without deterioration of the sensitivity. The use of an array of
nanodiamonds embedded within a portably polydimethylsiloxane (PDMS) sheet
provides a versatile temperature sensing platform that can probe a wide variety
of systems without the configurational restrictions needed for applying
microwaves. With this device, we observe a temperature gradient over tens of
microns in a ferromagnetic-insulator substrate (YIG) under local heating by a
resistive heater. This thermometry technique provides a cryogenically
compatible, microwave-free, minimally invasive approach capable of probing
local temperatures with few restrictions on the substrate materials.",1903.01605v1
2019-03-10,Magnons at low excitations: Observation of incoherent coupling to a bath of two-level-systems,"Collective magnetic excitation modes, magnons, can be coherently coupled to
microwave photons in the single excitation limit. This allows for access to
quantum properties of magnons and opens up a range of applications in quantum
information processing, with the intrinsic magnon linewidth representing the
coherence time of a quantum resonator. Our measurement system consists of a
yttrium iron garnet (YIG) sphere and a three-dimensional (3D) microwave cavity
at temperatures and excitation powers typical for superconducting quantum
circuit experiments. We perform spectroscopic measurements to determine the
limiting factor of magnon coherence at these experimental conditions. Using the
input-output formalism, we extract the magnon linewidth $\kappa_\mathrm{m}$. We
attribute the limitations of the coherence time at lowest temperatures and
excitation powers to incoherent losses into a bath of near-resonance two-level
systems (TLSs), a generic loss mechanism known from superconducting circuits
under these experimental conditions. We find that the TLSs saturate when
increasing the excitation power from quantum excitation to multi-photon
excitation and their contribution to the linewidth vanishes. At higher
temperatures, the TLSs saturate thermally and the magnon linewidth decreases as
well.",1903.03981v3
2019-03-22,Effects of post-deposition annealing on the structure and magnetization of PLD grown Yttrium Iron Garnet films,"We report on the recrystallization of 200 nm thick as-grown Yttrium Iron
Garnet (Y_3.4 Fe_4.6 O_12) films on (111) face of Gadolinium Gallium Garnet
(GGG) single crystals by post-deposition annealing. Epitaxial conversion of the
as-grown microcrystalline YIG films was seen after annealing at 800oC for more
than 30 minutes both in ambient oxygen as well as in air. The as-grown oxygen
annealed samples at 800oC for 60 minutes crystallize epitaxially and show
excellent figure-of-merit for saturation magnetization (MS = 3.3 {\mu}B/f.u.,
comparable to bulk value) and coercivity (HC ~ 1.1 Oe). The ambient air
annealing at 800oC with a very slow rate of cooling (2oC/min) results in a
double layer structure with a thicker unstrained epitaxial top layer having the
MS and HC of 2.9 {\mu}B/f.u. and 0.12 Oe respectively. The symmetric and
asymmetric Reciprocal space maps of both the samples reveal a locking of the
in-plane lattice of the film to the in-plane lattice of substrate, indicating a
pseudomorphic growth. The residual stress calculated by sin^2 {\psi} technique
is compressive in nature. The lower layer in air annealed sample is highly
strained, whereas, the top layer has negligible compressive stress.",1903.09457v1
2019-05-17,High-efficiency triple-resonant inelastic light scattering in planar optomagnonic cavities,"Optomagnonic cavities have recently been emerging as promising candidates for
implementing coherent microwave-to-optical conversion, quantum memories and
devices, and next generation quantum networks. A key challenge in the design of
such cavities is the attainment of high efficiencies, which could, e.g., be
exploited for efficient optical interfacing of superconducting qubits, as well
as the practicality of the final designs, which ideally should be planar and
amenable to on-chip integration. Here, on the basis of a novel time Floquet
scattering-matrix approach, we report on the design and optimization of a
planar, multilayer optomagnonic cavity, incorporating a Ce:YIG thin film,
magnetized in-plane, operating in the triple-resonant inelastic light
scattering regime. This architecture allows for conversion efficiencies of
about 5%, under realistic conditions, which is orders of magnitude higher than
alternative designs. Our results suggest a viable way forward for realizing
practical information inter-conversion between microwave photons and optical
photons, mediated by magnons, with efficiencies intrinsically greater than
those achieved in optomechanics and alternative related technologies, as well
as a platform for fundamental studies of classical and quantum dynamics in
magnetic solids, and implementation of futuristic quantum devices.",1905.07278v1
2019-11-01,Role of spin mixing conductance in determining thermal spin pumping near the ferromagnetic phase transition in EuO_{1-x} and La2NiMnO6,"We present a comprehensive study of the temperature (T) dependence of the
longitudinal spin Seebeck effect (LSSE) in Pt/EuO_{1-x} and Pt/La2NiMnO6 (LNMO)
hybrid structures across their Curie temperatures (Tc). Both systems host
ferromagnetic interaction below Tc, hence present optimal conditions for
testing magnon spin current based theories against ferrimagnetic YIG. Notably,
we observe an anomalous Nernst effect (ANE) generated voltage in bare
EuO_{1-x}, however, we find LSSE predominates the thermal signals in the
bilayers with Pt. The T-dependence of the LSSE in small T-range near Tc could
be fitted to a power law of the form (Tc-T)^P. The derived critical exponent,
P, was verified for different methods of LSSE representation and sample
crystallinity. The results are explained based on the magnon-driven thermal
spin pumping mechanism that relate the T-dependence of LSSE to the spin mixing
conductance (Gmix) at the heavy metal/ferromagnet (HM/FM) interface, which in
turn is known to vary in accordance with the square of the spontaneous
magnetization (Ms). Additionally, the T-dependence of the real part of Gmix
derived from spin Hall magnetoresistance measurements at different temperatures
for the Pt/LNMO structure, further establish the interdependence.",1911.00211v1
2020-01-24,Axion search with a quantum-limited ferromagnetic haloscope,"A ferromagnetic axion haloscope searches for Dark Matter in the form of
axions by exploiting their interaction with electronic spins. It is composed of
an axion-to-electromagnetic field transducer coupled to a sensitive rf
detector. The former is a photon-magnon hybrid system, and the latter is based
on a quantum-limited Josephson parametric amplifier. The hybrid system consists
of ten 2.1 mm diameter YIG spheres coupled to a single microwave cavity mode by
means of a static magnetic field. Our setup is the most sensitive rf
spin-magnetometer ever realized. The minimum detectable field is
$5.5\times10^{-19}\,$T with 9 h integration time, corresponding to a limit on
the axion-electron coupling constant $g_{aee}\le1.7\times10^{-11}$ at 95% CL.
The scientific run of our haloscope resulted in the best limit on DM-axions to
electron coupling constant in a frequency span of about 120 MHz, corresponding
to the axion mass range $42.4$-$43.1\,\mu$eV. This is also the first apparatus
to perform an axion mass scanning by changing the static magnetic field.",2001.08940v1
2020-01-31,Temperature dependence of spin pinning and spin-wave dispersion in nanoscopic ferromagnetic waveguides,"The field of magnonics attracts significant attention due to the possibility
of utilizing information coded into the spin-wave phase or amplitude to perform
computation operations on the nanoscale. Recently, spin waves were investigated
in Yttrium Iron Garnet (YIG) waveguides with widths ranging down to 50 nm and
aspect ratios thickness over width approaching unity. A critical width was
found, below which the exchange interaction suppresses the dipolar pinning
phenomenon and the system becomes unpinned. Here we continue these
investigations and analyse the pinning phenomenon and spin-wave dispersions as
a function of temperature, thickness and material of choice. Higher order
modes, the influence of a finite wavevector along the waveguide and the impact
of the pinning phenomenon on the spin-wave lifetime are discussed as well as
the influence of a trapezoidal cross section and edge roughness of the
waveguides. The presented results are of particular interest for potential
applications in magnonic devices and the incipient field of quantum magnonics
at cryogenic temperatures.",2002.00003v1
2020-04-16,A Magnon Scattering Platform,"Scattering experiments have revolutionized our understanding of nature.
Examples include the discovery of the nucleus, crystallography, and the
discovery of the double helix structure of DNA. Scattering techniques differ by
the type of the particles used, the interaction these particles have with
target materials and the range of wavelengths used. Here, we demonstrate a new
2-dimensional table-top scattering platform for exploring magnetic properties
of materials on mesoscopic length scales. Long lived, coherent magnonic
excitations are generated in a thin film of YIG and scattered off a magnetic
target deposited on its surface. The scattered waves are then recorded using a
scanning NV center magnetometer that allows sub-wavelength imaging and
operation under conditions ranging from cryogenic to ambient environment. While
most scattering platforms measure only the intensity of the scattered waves,
our imaging method allows for spatial determination of both amplitude and phase
of the scattered waves thereby allowing for a systematic reconstruction of the
target scattering potential. Our experimental results are consistent with
theoretical predictions for such a geometry and reveal several unusual features
of the magnetic response of the target, including suppression near the target
edges and gradient in the direction perpendicular to the direction of surface
wave propagation. Our results establish magnon scattering experiments as a new
platform for studying correlated many-body systems.",2004.07763v1
2020-05-18,The Einstein - de Haas effect at radio frequencies in and near magnetic equilibrium,"The Einstein-de Haas (EdH) effect and its reciprocal the Barnett effect are
fundamental to magnetism and uniquely yield measures of the ratio of magnetic
moment to total angular momentum. These effects, small and generally difficult
to observe, are enjoying a resurgence of interest as contemporary techniques
enable new approaches to their study. The high mechanical resonance frequencies
in nanomechanical systems offer a tremendous advantage for the observation of
EdH torques in particular. At radio frequencies, the EdH effect can become
comparable to or even exceed in magnitude conventional cross-product magnetic
torques. In addition, the RF-EdH torque is expected to be phase-shifted by 90
degrees relative to cross-product torques, provided the magnetic system remains
in quasi-static equilibrium, enabling separation in quadratures when both
sources of torque are operative. Radio frequency EdH measurements are
demonstrated through the full hysteresis range of micrometer scale,
monocrystalline yttrium iron garnet (YIG) disks. Equilibrium behavior is
observed in the vortex state at low bias field. Barkhausen-like features emerge
in the in-plane EdH torque at higher fields in the vortex state, revealing
magnetic disorder too weak to be visible through the in-plane cross-product
torque. Beyond vortex annihilation, peaks arise in the EdH torque versus bias
field, and these together with their phase signatures indicate additional
utility of the Einstein-de Haas effect for the study of RF-driven spin
dynamics.",2005.08406v1
2020-07-17,Coherent coupling between multiple ferrimagnetic spheres and a microwave cavity in the quantum-limit,"The spin resonance of electrons can be coupled to a microwave cavity mode to
obtain a photon-magnon hybrid system. These quantum systems are widely studied
for both fundamental physics and technological quantum applications. In this
article, the behavior of a large number of ferrimagnetic spheres coupled to a
single cavity is put under test. We use second-quantization modeling of
harmonic oscillators to theoretically describe our experimental setup and
understand the influence of several parameters. The magnon-polariton dispersion
relation is used to characterize the system, with a particular focus on the
vacuum Rabi mode splitting due to multiple spheres. We combine the results
obtained with simple hybrid systems to analyze the behavior of a more complex
one, and show that it can be devised in such a way to minimize the degrees of
freedom needed to completely describe it. By studying single-sphere coupling
two possible size-effects related to the sample diameter have been identified,
while multiple-spheres configurations reveal how to upscale the system. This
characterization is useful for the implementation of an
axion-to-electromagnetic field transducer in a ferromagnetic haloscope for dark
matter searches. Our dedicated setup, consisting in ten 2 mm-diameter YIG
spheres coupled to a copper microwave cavity, is used for this aim and studied
at mK temperatures. Moreover, we show that novel applications of
optimally-controlled hybrid systems can be foreseen for setups embedding a
large number of samples.",2007.08908v3
2021-02-26,Control of the Bose-Einstein Condensation of Magnons by the Spin-Hall Effect,"Previously, it has been shown that rapid cooling of yttrium-iron-garnet
(YIG)/platinum (Pt) nano structures, preheated by an electric current sent
through the Pt layer, leads to overpopulation of a magnon gas and to subsequent
formation of a Bose-Einstein condensate (BEC) of magnons. The spin Hall effect
(SHE), which creates a spin-polarized current in the Pt layer, can inject or
annihilate magnons depending on the electric current and applied field
orientations. Here we demonstrate that the injection or annihilation of magnons
via the SHE can prevent or promote the formation of a rapid cooling induced
magnon BEC. Depending on the current polarity, a change in the BEC threshold of
-8% and +6% was detected. These findings demonstrate a new method to control
macroscopic quantum states, paving the way for their application in spintronic
devices.",2102.13481v2
2021-07-14,Sublattice spin reversal and field induced $Fe^{3+}$ spin-canting across the magnetic compensation temperature in $Y_{1.5}Gd_{1.5}Fe_{5}O_{12}$ rare-earth iron garnet,"In the present work $Fe^{3+}$ sublattice spin reversal and $Fe^{3+}$
spin-canting across the magnetic compensation temperature ($T_{Comp}$) are
demonstrated in polycrystalline $Y_{1.5}Gd_{1.5}Fe_{5}O_{12}$ (YGdIG) by means
of in-field $^{57}Fe$ M$\ddot{o}$ssbauer spectroscopy measurements.
Corroborating in-field $^{57}Fe$ M$\ddot{o}$ssbauer measurements, both
$Fe^{3+}$ & $Gd^{3+}$ sublattice spin reversal has also been manifested with
x-ray magnetic circular dichroism (XMCD) measurement in hard x-ray region.
Moreover from in-field $^{57}Fe$ M$\ddot{o}$ssbauer measurements, estimation
and analysis of effective internal hyperfine field ($H_{eff}$), relative
intensity of absorption lines in a sextet elucidated unambiguously the
signatures of $Fe^{3+}$ spin reversal, their continuous transition and field
induced spin-canting of $Fe^{3+}$ sublattices across $T_{Comp}$. Further, Fe K-
(Gd $L_{3}$-) edge XMCD signal is observed to consist of additional spectral
features, those are identified from $Gd^{3+}$ ($Fe^{3+}$) magnetic ordering,
enabling us the extraction of both the sublattices ($Fe^{3+}$ & $Gd^{3+}$)
information from a single edge analysis. The evolution of the magnetic moments
as a function of temperature for both magnetic sublattices extracted either at
the Fe K- or Gd $L_3$-edge agree quite well with values that are extracted from
bulk magnetization data of YGdIG and YIG ($Y_{3}Fe_{5}O_{12}$). These
measurements pave new avenues to investigate how the magnetic behavior of such
complex system acts across the compensation point.",2107.06508v3
2021-07-20,Spin-wave dispersion measurement by variable-gap propagating spin-wave spectroscopy,"Magnonics is seen nowadays as a candidate technology for energy-efficient
data processing in classical and quantum systems. Pronounced nonlinearity,
anisotropy of dispersion relations and phase degree of freedom of spin waves
require advanced methodology for probing spin waves at room as well as at mK
temperatures. Yet, the use of the established optical techniques like Brillouin
light scattering (BLS) or magneto optical Kerr effect (MOKE) at ultra-low
temperatures is forbiddingly complicated. By contrast, microwave spectroscopy
can be used at all temperatures but is usually lacking spatial and wavenumber
resolution. Here, we develop a variable-gap propagating spin-wave spectroscopy
(VG-PSWS) method for the deduction of the dispersion relation of spin waves in
wide frequency and wavenumber range. The method is based on the phase-resolved
analysis of the spin-wave transmission between two antennas with variable
spacing, in conjunction with theoretical data treatment. We validate the method
for the in-plane magnetized CoFeB and YIG thin films in $k\perp B$ and
$k\parallel B$ geometries by deducing the full set of material and spin-wave
parameters, including spin-wave dispersion, hybridization of the fundamental
mode with the higher-order perpendicular standing spin-wave modes and surface
spin pinning. The compatibility of microwaves with low temperatures makes this
approach attractive for cryogenic magnonics at the nanoscale.",2107.09363v1
2021-08-02,Circular displacement current induced anomalous magneto-optical effects in high index Mie resonators,"Dielectric Mie nanoresonators showing strong light-matter interaction at the
nanoscale may enable new functionality in photonic devices. Recently, strong
magneto-optical effects have been observed in magneto-optical nanophotonic
devices due to the electromagnetic field localization. However, most reports so
far have been focused on the enhancement of conventional magneto-optical
effects. Here, we report the observation of circular displacement current
induced anomalous magneto-optical effects in high-index-contrast
Si/Ce:YIG/YIG/SiO2 Mie resonators. In particular, giant modulation of light
intensity in transverse magnetic configuration up to 6.4 % under s-polarized
incidence appears, which is non-existent in planar magneto-optical thin films.
Apart from that, we observe a large rotation of transmitted light polarization
in the longitudinal magnetic configuration under near normal incidence
conditions, which is two orders of magnitude higher than for a planar
magneto-optical thin film. These phenomena are essentially originated from the
unique circular displacement current when exciting the magnetic resonance modes
in the Mie resonators, which changes the incident electric field direction
locally. Our work indicates an uncharted territory of light polarization
control based on the complex modal profiles in all-dielectric magneto-optical
Mie resonators and metasurfaces, which opens the door for versatile control of
light propagation by magnetization for a variety of applications in vectoral
magnetic field and biosensing, free space non-reciprocal photonic devices,
magneto-optical imaging and optomagnetic memories.",2108.00615v1
2021-07-14,Broadband energy squeezing and tunneling based on unidirectional modes,"Energy squeezing attracts many attentions for its potential applications in
electromagnetic (EM) energy harvesting and optical communication. However, due
to the Fabry-Perot resonance, only the EM waves with discrete frequencies can
be squeezed and, as far as we know, in the previous energy-squeezing devices,
stringent requirements of the materials or the geometrical shape are needed. We
note that the structures filled with epsilon-near-zero (ENZ) mediums as
reported in some works can squeeze and tunnel EM waves at frequencies (e.g.
plasma frequency). However, the group velocity is usually near zero which means
few EM information travel through the structures. In this paper, low-loss
energy squeezing and tunneling (EST) based on unidirectional modes were
demonstrated in YIG-based one-way waveguides at microwave frequencies.
According to our theoretical analysis and the simulations using finite element
method, broadband EST was achieved and the EM EST was observed even for
extremely bended structures. Besides, similar EM EST was achieved in a
realistic three-dimensional remanence-based one-way waveguide as well. The
unidirectional modes-based EST paving the way to ultra-subwavelength EM
focusing, enhanced nonlinear optics, and designing numerous functional devices
in integrated optical circuits such as phase modulator.",2108.04196v1
2022-01-23,Squeezed driving induced entanglement and squeezing among cavity modes and magnon mode in a magnon-cavity QED system,"We propose a scheme to generate entanglement between two cavity modes and
squeeze magnon mode in a magnon-cavity QED system, where the two microwave
cavity modes are coupled with a massive yttrium iron garnet (YIG) sphere
through magnetic dipole interaction. The nonlinearity used in our system
originates from a squeezed driving via parametric down-conversion process,
which is the reason to cause entanglement and squeezing. By using the mean
field approximation and employing experimentally feasible parameters, we
demonstrate that the system shows zero entanglement and squeezing without
squeezed driving. Meanwhile, our QED system denotes that the entanglement
between squeezed cavity mode and magnon mode can be transferred to the other
cavity mode and magnon mode via magnon-cavity coupling interaction, and then
the two cavity modes get entangled. A genuinely tripartite entangled state is
formed. We also show that magnon mode can be prepared in a squeezed state via
magnon-cavity beam-splitter interaction, which is as a result of the squeezed
field. Moreover, we show that it is a good way to enhance entanglement and
squeezing by increasing the nonlinear gain coefficient of squeezed driving. Our
results denote that magnon-cavity QED system is a powerful platform for
studying macroscopic quantum phenomena, which illustrates a new method to
photon-photon entanglement and magnon squeezing.",2201.09154v1
2022-03-12,Observation of nonlinear planar Hall effect in magnetic insulator/topological insulator heterostructures,"Interfacing topological insulators (TIs) with magnetic insulators (MIs) has
been widely used to study the interaction between topological surface states
and magnetism. Previous transport studies typically interpret the suppression
of weak antilocalization or appearance of the anomalous Hall effect as
signatures of magnetic proximity effect (MPE) imposed to TIs. Here, we report
the observation of nonlinear planar Hall effect (NPHE) in Bi2Se3 films grown on
MI thulium and yttrium iron garnet (TmIG and YIG) substrates, which is an order
of magnitude larger than that in Bi2Se3 grown on nonmagnetic gadolinium gallium
garnet (GGG) substrate. The nonlinear Hall resistance in TmIG/Bi2Se3 depends
linearly on the external magnetic field, while that in YIG/Bi2Se3 exhibits an
extra hysteresis loop around zero field. The magnitude of the NPHE is found to
scale inversely with carrier density. We speculate the observed NPHE is related
to the MPE-induced exchange gap opening and out-of-plane spin textures in the
TI surface states, which may be used as an alternative transport signature of
the MPE in MI/TI heterostructures.",2203.06293v2
2023-01-13,Voltage-Controlled Magnon Transistor via Tunning Interfacial Exchange Coupling,"Magnon transistors that can effectively regulate magnon transport by an
electric field are desired for magnonics which aims to provide a Joule-heating
free alternative to the conventional electronics owing to the electric
neutrality of magnons (the key carriers of spin-angular momenta in the
magnonics). However, also due to their electric neutrality, magnons have no
access to directly interact with an electric field and it is thus difficult to
manipulate magnon transport by voltages straightforwardly. Here, we
demonstrated a gate voltage ($V_{\rm g}$) applied on a nonmagnetic
metal/magnetic insulator (NM/MI) interface that bended the energy band of the
MI and then modulated the possibility for conduction electrons in the NM to
tunnel into the MI can consequently enhance or weaken the spin-magnon
conversion efficiency at the interface. A voltage-controlled magnon transistor
based on the magnon-mediated electric current drag (MECD) effect in a
Pt/Y$_{\rm 3}$Fe$_{\rm 5}$O$_{\rm 12}$ (YIG)/Pt sandwich was then
experimentally realized with $V_{\rm g}$ modulating the magnitude of the MECD
signal. The obtained efficiency (the change ratio between the MECD voltage at
$\pm V_{\rm g}$) reached 10%/(MV/cm) at 300 K. This prototype of magnon
transistor offers an effective scheme to control magnon transport by a gate
voltage.",2301.05592v1
2023-02-02,Leveraging symmetry for an accurate spin-orbit torques characterization in ferrimagnetic insulators,"Spin-orbit torques (SOTs) have emerged as an efficient means to electrically
control the magnetization in ferromagnetic heterostructures. Lately, an
increasing attention has been devoted to SOTs in heavy metal (HM)/magnetic
insulator (MI) bilayers owing to their tunable magnetic properties and
insulating nature. Quantitative characterization of SOTs in HM/MI
heterostructures are, thus, vital for fundamental understanding of charge-spin
interrelations and designing novel devices. However, the accurate determination
of SOTs in MIs have been limited so far due to small electrical signal outputs
and dominant spurious thermoelectric effects caused by Joule heating. Here, we
report a simple methodology based on harmonic Hall voltage detection and
macrospin simulations to accurately quantify the damping-like and field-like
SOTs, and thermoelectric contributions separately in MI-based systems.
Experiments on the archetypical Bi-doped YIG/Pt heterostructure using the
developed method yield precise values for the field-like and damping-like SOTs,
reaching -0.14 and -0.15 mT per 1.7x$10^{ 11}$ A/$m^2$, respectively. We
further reveal that current-induced Joule heating changes the spin transparency
at the interface, reducing the spin Hall magnetoresistance and damping-like
SOT, simultaneously. These results and the devised method can be beneficial for
fundamental understanding of SOTs in MI-based heterostructures and designing
new devices where accurate knowledge of SOTs is necessary.",2302.01141v2
2023-03-07,Magnon currents excited by the spin Seebeck effect in ferromagnetic EuS thin films,"A magnetic insulator is an ideal platform to propagate spin information by
exploiting magnon currents. However, until now, most studies have focused on
Y$_3$Fe$_5$O$_{12}$ (YIG) and a few other ferri- and antiferromagnetic
insulators, but not on pure ferromagnets. In this study, we demonstrate for the
first time that magnon currents can propagate in ferromagnetic insulating thin
films of EuS. By performing both local and non-local transport measurements in
18-nm-thick films of EuS using Pt electrodes, we detect magnon currents arising
from thermal generation by the spin Seebeck effect. By comparing the dependence
of the local and non-local signals with the temperature (< 30 K) and magnetic
field (< 9 T), we confirm the magnon transport origin of the non-local signal.
Finally, we extract the magnon diffusion length in the EuS film (~140 nm), a
short value in good correspondence with the large Gilbert damping measured in
the same film.",2303.03833v2
2023-04-21,Magnon squeezing by two-tone driving of a qubit in cavity-magnon-qubit systems,"We propose a scheme for preparing magnon squeezed states in a hybrid
cavity-magnon-qubit system. The system consists of a microwave cavity that
simultaneously couples to a magnon mode of a macroscopic yttrium-iron-garnet
(YIG) sphere via the magnetic-dipole interaction and to a transmon-type
superconducting qubit via the electric-dipole interaction. By far detuning from
the magnon-qubit system, the microwave cavity is adiabatically eliminated. The
magnon mode and the qubit then get effectively coupled via the mediation of
virtual photons of the microwave cavity. We show that by driving the qubit with
two microwave fields and by appropriately choosing the drive frequencies and
strengths, magnonic parametric amplification can be realized, which leads to
magnon quadrature squeezing with the noise below vacuum fluctuation. We provide
optimal conditions for achieving magnon squeezing, and moderate squeezing can
be obtained using currently available parameters. The generated squeezed states
are of a magnon mode involving more than $10^{18}$ spins and thus macroscopic
quantum states. The work may find promising applications in quantum information
processing and high-precision measurements based on magnons and in the study of
macroscopic quantum states.",2304.10760v4
2023-07-12,Quantum information diode based on a magnonic crystal,"Exploiting the effect of nonreciprocal magnons in a system with no inversion
symmetry, we propose a concept of a quantum information diode, {\it i.e.}, a
device rectifying the amount of quantum information transmitted in the opposite
directions. We control the asymmetric left and right quantum information
currents through an applied external electric field and quantify it through the
left and right out-of-time-ordered correlation (OTOC). To enhance the
efficiency of the quantum information diode, we utilize a magnonic crystal. We
excite magnons of different frequencies and let them propagate in opposite
directions. Nonreciprocal magnons propagating in opposite directions have
different dispersion relations. Magnons propagating in one direction match
resonant conditions and scatter on gate magnons. Therefore, magnon flux in one
direction is damped in the magnonic crystal leading to an asymmetric transport
of quantum information in the quantum information diode. A quantum information
diode can be fabricated from an yttrium iron garnet (YIG) film. This is an
experimentally feasible concept and implies certain conditions: low temperature
and small deviation from the equilibrium to exclude effects of phonons and
magnon interactions. We show that rectification of the flaw of quantum
information can be controlled efficiently by an external electric field and
magnetoelectric effects.",2307.06047v1
2023-07-14,Magnonic Combinatorial Memory,"In this work, we consider a type of magnetic memory where information is
encoded into the mutual arrangements of magnets. The device is an active ring
circuit comprising magnetic and electronic parts connected in series. The
electric part includes a broad-band amplifier, phase shifters, and attenuators.
The magnetic part is a mesh of magnonic waveguides with magnets placed on the
waveguide junctions. There are amplitude and phase conditions for
auto-oscillations to occur in the active ring circuit. The frequency(s) of the
auto-oscillation and spin wave propagation route(s) in the magnetic part
depends on the mutual arrangement of magnets in the mesh. The propagation route
is detected with a set of power sensors. The correlation between circuit
parameters and spin wave route is the base of memory operation. The combination
of input/output switches connecting electric and magnetic parts, and electric
phase shifters constitute the memory address. The output of power sensors is
the memory state. We present experimental data on the proof-of-the-concept
experiments on the prototype with just three magnets placed on top of a
single-crystal yttrium iron garnet Y3Fe2(FeO4)3 (YIG) film. The results
demonstrate a robust operation with On/Off ratio for route detection exceeding
35 dB at room temperature. The number of propagation routes scales factorial
with the size of the magnetic part. Coding information in propagation routes
makes it possible to drastically increase the data storage density compared to
conventional memory devices. MCM with just 25 magnets can store as much as 25!
(10 Yotta) bits. Physical limits and constraints are also discussed.",2307.07464v1
2023-12-15,Magnon Bose-Einstein condensates: from time crystals and quantum chromodynamics to vortex sensing and cosmology,"Under suitable experimental conditions collective spin-wave excitations,
magnons, form a Bose-Einstein condensate (BEC) where the spins precess with a
globally coherent phase. Bose-Einstein condensation of magnons has been
reported in a few systems, including superfluid phases of $^3$He, solid state
systems such as Yttrium-iron-garnet (YIG) films, and cold atomic gases. Among
these systems, the superfluid phases of $^3$He provide a nearly ideal test
bench for coherent magnon physics owing to experimentally proven spin
superfluidity, the long lifetime of the magnon condensate, and the versatility
of the accessible phenomena. We first briefly recap the properties of the
different magnon BEC systems, with focus on superfluid $^3$He. The main body of
this review summarizes recent advances in application of magnon BEC as a
laboratory to study basic physical phenomena connecting to diverse areas from
particle physics and cosmology to new phases of condensed matter. This line of
research complements the ongoing efforts to utilize magnon BECs as probes and
components for potentially room-temperature quantum devices. In conclusion, we
provide a roadmap for future directions in the field of applications of magnon
BEC to fundamental research.",2312.10119v1
2024-01-04,Nonreciprocal photon blockade with Kerr magnons,"Nonreciprocal devices, allowing to manipulate one-way signals, are crucial to
quantum information processing and quantum network. Here we propose a nonlinear
cavity-magnon system, consisting of a microwave cavity coupled to one or two
yttrium-iron-garnet (YIG) spheres supporting magnons with Kerr nonlinearity, to
investigate nonreciprocal photon blockade. The nonreciprocity originates from
the direction-dependent Kerr effect, distinctly different from previous
proposals with spinning cavities and dissipative couplings. For a single sphere
case, nonreciprocal photon blockade can be realized by manipulating the
nonreciprocal destructive interference between two active paths, via vary the
Kerr coefficient from positive to negative, or vice versa. By optimizing the
system parameters, the perfect and well tuned nonreciprocal photon blockade can
be predicted. For the case of two spheres with opposite Kerr effects, only
reciprocal photon blockade can be observed when two cavity-magnon coupling
strengths Kerr strengths are symmetric. However, when coupling strengths or
Kerr strengths become asymmetric, nonreciprocal photon blockade appears. This
implies that two-sphere nonlinear cavity-magnon systems can be used to switch
the transition between reciprocal and nonreciprocal photon blockades. Our study
offers a potential platform for investigating nonreciprocal photon blockade
effect in nonlinear cavity magnonics.",2401.02251v1
2024-02-06,Magnon mediated spin pumping by coupled ferrimagnetic garnets heterostructure,"Spin pumping has significant implications for spintronics, providing a
mechanism to manipulate and transport spins for information processing.
Understanding and harnessing spin currents through spin pumping is critical for
the development of efficient spintronic devices. The use of a magnetic
insulator with low damping, enhances the signal-to-noise ratio in crucial
experiments such as spin-torque ferromagnetic resonance (FMR) and spin pumping.
A magnetic insulator coupled with a heavy metal or quantum material offers a
more straight forward model system, especially when investigating spin-charge
interconversion processes to greater accuracy. This simplicity arises from the
absence of unwanted effects caused by conduction electrons unlike in
ferromagnetic metals. Here, we investigate the spin pumping in coupled
ferrimagnetic (FiM) Y3Fe5O12 (YIG)/Tm3Fe5O12 (TmIG) bilayers combined with
heavy-metal (Pt) using the inverse spin Hall effect (ISHE). It is observed that
magnon transmission occurs at both of the FiMs FMR positions. The enhancement
of spin pumping voltage (Vsp) in the FiM garnet heterostructures is attributed
to the strong interfacial exchange coupling between FiMs. The modulation of Vsp
is achieved by tuning the bilayer structure. Further, the spin mixing
conductance for these coupled systems is found to be 10^18 m^-2. Our findings
describe a novel coupled FiM system for the investigation of magnon coupling
providing new prospects for magnonic devices.",2402.03734v1
2001-09-19,Solid State Systems for Electron Electric Dipole Moment and other Fundamental Measurements,"In 1968, F.L. Shapiro published the suggestion that one could search for an
electron EDM by applying a strong electric field to a substance that has an
unpaired electron spin; at low temperature, the EDM interaction would lead to a
net sample magnetization that can be detected with a SQUID magnetometer. One
experimental EDM search based on this technique was published, and for a number
of reasons including high sample conductivity, high operating temperature, and
limited SQUID technology, the result was not particularly sensitive compared to
other experiments in the late 1970's.
  Advances in SQUID and conventional magnetometery had led us to reconsider
this type of experiment, which can be extended to searches and tests other than
EDMs (e.g., test of Lorentz invariance). In addition, the complementary
measurement of an EDM-induced sample electric polarization due to application
of a magnetic field to a paramagnetic sample might be effective using modern
ultrasensitive charge measurement techniques. A possible paramagnetic material
is Gd-substituted YIG which has very low conductivity and a net enhancement
(atomic enhancement times crystal screening) of order unity. Use of a
reasonable volume (100's of cc) sample of this material at 50 mK and 10 kV/cm
might yield an electron EDM sensitivity of $10^{-33}$ e cm or better, a factor
of $10^6$ improvement over current experimental limits.",0109014v4
2016-12-21,Bose-Einstein Condensation of Quasi-Particles by Rapid Cooling,"The fundamental phenomenon of Bose-Einstein Condensation (BEC) has been
observed in different systems of real and quasi-particles. The condensation of
real particles is achieved through a major reduction in temperature while for
quasi-particles a mechanism of external injection of bosons by irradiation is
required. Here, we present a novel and universal approach to enable BEC of
quasi-particles and to corroborate it experimentally by using magnons as the
Bose-particle model system. The critical point to this approach is the
introduction of a disequilibrium of magnons with the phonon bath. After heating
to an elevated temperature, a sudden decrease in the temperature of the
phonons, which is approximately instant on the time scales of the magnon
system, results in a large excess of incoherent magnons. The consequent
spectral redistribution of these magnons triggers the Bose-Einstein
condensation.",1612.07305v3
2018-01-04,Complex temperature dependence of coupling and dissipation of cavity-magnon polaritons from milliKelvin to room temperature,"Hybridized magnonic-photonic systems are key components for future
information processing technologies such as storage, manipulation or conversion
of data both in the classical (mostly at room temperature) and quantum
(cryogenic) regime. In this work, we investigate a YIG sphere coupled strongly
to a microwave cavity over the full temperature range from $290\,\mathrm{K}$
down to $30\,\mathrm{mK}$. The cavity-magnon polaritons are studied from the
classical to the quantum regime where the thermal energy is less than one
resonant microwave quanta, i.e. at temperatures below $1\,\mathrm{K}$. We
compare the temperature dependence of the coupling strength $g_{\rm{eff}}(T)$,
describing the strength of coherent energy exchange between spin ensemble and
cavity photon, to the temperature behavior of the saturation magnetization
evolution $M_{\rm{s}}(T)$ and find strong deviations at low temperatures. The
temperature dependence of magnonic disspation is governed at intermediate
temperatures by rare earth impurity scattering leading to a strong peak at
$40\,$K. The linewidth $\kappa_{\rm{m}}$ decreases to $1.2\,$MHz at $30\,$mK,
making this system suitable as a building block for quantum electrodynamics
experiments. We achieve an electromagnonic cooperativity in excess of $20$ over
the entire temperature range, with values beyond $100$ in the milliKelvin
regime as well as at room temperature. With our measurements, spectroscopy on
strongly coupled magnon-photon systems is demonstrated as versatile tool for
spin material studies over large temperature ranges. Key parameters are
provided in a single measurement, thus simplifying investigations
significantly.",1801.01439v1
2021-09-09,A low-power integrated magneto-optic modulator on silicon for cryogenic applications,"A fundamental challenge of the quantum revolution is to efficiently interface
the quantum computing systems operating at cryogenic temperatures with room
temperature electronics and media for high data-rate communication. Current
approaches to control and readout of such cryogenic computing systems use
electrical cables, which prevent scalability due to their large size, heat
conduction, and limited bandwidth1. A more viable approach is to use optical
fibers which allow high-capacity transmission and thermal isolation. A key
component in implementing photonic datalinks is a cryogenic optical modulator
for converting data from the electrical to the optical domain at high speed and
with low power consumption, while operating at temperatures of 4 K or lower.
Cryogenic modulators based on the electro-optic effect have been demonstrated
in a variety of material platforms, however they are voltage driven components
while superconducting circuits are current based, resulting in a large
impedance mismatch. Here, we present the first demonstration of an integrated
current-driven modulator based on the magneto-optic effect operating over a
wide temperature range that extends down to less than 4 K. The modulator works
at data rates up to 2 Gbps with energy consumption below 4 pJ/bit, and we show
that this figure can be reduced to less than 40 fJ/bit with optimized design
and fabrication. This modulator is a hybrid device, where a current-driven
magneto-optically active crystal (cerium substituted yttrium iron garnet, or
Ce:YIG) is bonded to a high-quality silicon microring resonator. Because of its
potential for extremely low power consumption under cryogenic conditions, the
class of magneto-optical modulators demonstrated here has the potential to
enable efficient data links in large-scale systems for quantum information
processing.",2109.04538v1
2021-10-11,Transition of laser-induced terahertz spin currents from torque- to conduction-electron-mediated transport,"Spin transport is crucial for future spintronic devices operating at
bandwidths up to the terahertz (THz) range. In F|N thin-film stacks made of a
ferro/ferrimagnetic layer F and a normal-metal layer N, spin transport is
mediated by (1) spin-polarized conduction electrons and/or (2) torque between
electron spins. To identify a cross-over from (1) to (2), we study laser-driven
spin currents in F|Pt stacks where F consists of model materials with different
degrees of electrical conductivity. For the magnetic insulators YIG, GIG and
maghemite, identical dynamics is observed. It arises from the THz interfacial
spin Seebeck effect (SSE), is fully determined by the relaxation of the
electrons in the metal layer and provides an estimate of the spin-mixing
conductance of the GIG/Pt interface. Remarkably, in the half-metallic
ferrimagnet Fe3O4 (magnetite), our measurements reveal two spin-current
components with opposite direction. The slower, positive component exhibits SSE
dynamics and is assigned to torque-type magnon excitation of the A- and B-spin
sublattices of Fe3O4. The faster, negative component arises from the
pyro-spintronic effect and can consistently be assigned to ultrafast
demagnetization of e-sublattice minority-spin hopping electrons. This
observation supports the magneto-electronic model of Fe3O4. In general, our
results provide a new route to the contact-free separation of torque- and
conduction-electron-mediated spin currents.",2110.05462v2
2023-06-28,Degenerate and non-degenerate parametric excitation in YIG nanostructures,"We study experimentally the processes of parametric excitation in microscopic
magnetically saturated disks of nanometer-thick Yttrium Iron Garnet. We show
that, depending on the relative orientation between the parametric pumping
field and the static magnetization, excitation of either degenerate or
non-degenerate magnon pairs is possible. In the latter case, which is
particularly important for applications associated with the realization of
computation in the reciprocal space, a single-frequency pumping can generate
pairs of magnons whose frequencies correspond to different eigenmodes of the
disk. We show that, depending on the size of the disk and the modes involved,
the frequency difference in a pair can vary in the range 0.1-0.8 GHz. We
demonstrate that in this system, one can easily realize a practically important
situation where several magnon pairs share the same mode. We also observe the
simultaneous generation of up to six different modes using a fixed-frequency
monochromatic pumping. Our experimental findings are supported by numerical
calculations that allow us to unambiguously identify the excited modes. Our
results open new possibilities for the implementation of reciprocal-space
computing making use of low damping magnetic insulators.",2306.16094v1
2023-08-07,$\textit{In situ}$ electric-field control of ferromagnetic resonance in the low-loss organic-based ferrimagnet V[TCNE]$_{x\sim 2}$,"We demonstrate indirect electric-field control of ferromagnetic resonance
(FMR) in devices that integrate the low-loss, molecule-based, room-temperature
ferrimagnet vanadium tetracyanoethylene (V[TCNE]$_{x \sim 2}$) mechanically
coupled to PMN-PT piezoelectric transducers. Upon straining the V[TCNE]$_x$
films, the FMR frequency is tuned by more than 6 times the resonant linewidth
with no change in Gilbert damping for samples with $\alpha = 6.5 \times
10^{-5}$. We show this tuning effect is due to a strain-dependent magnetic
anisotropy in the films and find the magnetoelastic coefficient $|\lambda_S|
\sim (1 - 4.4)$ ppm, backed by theoretical predictions from DFT calculations
and magnetoelastic theory. Noting the rapidly expanding application space for
strain-tuned FMR, we define a new metric for magnetostrictive materials,
$\textit{magnetostrictive agility}$, given by the ratio of the magnetoelastic
coefficient to the FMR linewidth. This agility allows for a direct comparison
between magnetostrictive materials in terms of their comparative efficacy for
magnetoelectric applications requiring ultra-low loss magnetic resonance
modulated by strain. With this metric, we show V[TCNE]$_x$ is competitive with
other magnetostrictive materials including YIG and Terfenol-D. This combination
of ultra-narrow linewidth and magnetostriction in a system that can be directly
integrated into functional devices without requiring heterogeneous integration
in a thin-film geometry promises unprecedented functionality for electric-field
tuned microwave devices ranging from low-power, compact filters and circulators
to emerging applications in quantum information science and technology.",2308.03353v1