United States

Non-reciprocal (NR) microwave components providing a unidirectional flow of energy are essential for signal processing. Spin waves (SWs) possess attractive
characteristics that make them commonly harnessed to design NR components. However these components are presently mainly ferrite-based and bulky; more compact and integrable
systems are desirable. Synthetic antiferromagnet (SAF) films with strong dipole-dipole interactions have been proposed [1] as a versatile platform on which strongly NR behaviors could be
obtained at micron-scale physical dimensions in the frequency range of their eigen excitations. We have studied the NR behavior of SWs in Co40Fe40B20 (17 nm) /Ru (0.7 nm)/CoFeB (17 nm) SAFs using inductive propagative spin wave spectroscopy, analytical modeling and
numerical micromagnetics using the mumax3 solftware. The films were patterned in 20 micron-wide stripes used as SW conduits. Two inductive antenna separated by a variable distance
[2-8 microns, Fig. 1(a)] are used to generate and collect the spin waves by means of a 2-port vector network analyzer. We determine the forward and backward transmission parameters for
variable applied fields and variable field-to-wavevector orientations. When the SAF is in the scissors state, all directions show substantial frequency and amplitude non-reciprocities (Fig.
1), except when the wavevector is perpendicular to the applied field, where only NR amplitude is observed. We model this behavior by computing the dispersion relation of the acoustical
and optical spin waves of the SAF and their sensitivity to the radio frequency (RF) fields of the antenna, as well the inductive transduction back to the electrical domain. We will show how
the dispersion relations and the symmetries of the susceptibility tensor can be used to design optimally NR transmission parameters.&lt;br&gt;
**References** &lt;br&gt;[1] Mio Ishibashi et al., Science Advances, 6, eaaz6931 (2020).&lt;br&gt;
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/f7dfce9480981a586fc0403aedb61d54.png)&lt;br&gt;
Fig. 1: (a) Device and geometrical conventions; (b) Reflection parameter of antenna 1, used to identify the frequencies of the acoustical and optical modes at k=0 (blue lines). (c) and (d)
forward and backward transmission parameters.&lt;br&gt;

MMM 2022

Electrical Evidence and Modeling of the Giant Non Reciprocity of Spin

Non-reciprocal (NR) microwave components providing a unidirectional flow of energy are essential for signal processing. Spin waves (SWs) possess attractive
characteristics that make them commonly harnessed to design NR components. However these components are presently mainly ferrite-based and bulky; more compact and integrable
systems are desirable. Synthetic antiferromagnet (SAF) films with strong dipole-dipole interactions have been proposed [1] as a versatile platform on which strongly NR behaviors could be
obtained at micron-scale physical dimensions in the frequency range of their eigen excitations. We have studied the NR behavior of SWs in Co40Fe40B20 (17 nm) /Ru (0.7 nm)/CoFeB (17 nm) SAFs using inductive propagative spin wave spectroscopy, analytical modeling and
numerical micromagnetics using the mumax3 solftware. The films were patterned in 20 micron-wide stripes used as SW conduits. Two inductive antenna separated by a variable distance
[2-8 microns, Fig. 1(a)] are used to generate and collect the spin waves by means of a 2-port vector network analyzer. We determine the forward and backward transmission parameters for
variable applied fields and variable field-to-wavevector orientations. When the SAF is in the scissors state, all directions show substantial frequency and amplitude non-reciprocities (Fig.
1), except when the wavevector is perpendicular to the applied field, where only NR amplitude is observed. We model this behavior by computing the dispersion relation of the acoustical
and optical spin waves of the SAF and their sensitivity to the radio frequency (RF) fields of the antenna, as well the inductive transduction back to the electrical domain. We will show how
the dispersion relations and the symmetries of the susceptibility tensor can be used to design optimally NR transmission parameters. 
**References** [1] Mio Ishibashi et al., Science Advances, 6, eaaz6931 (2020). 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/f7dfce9480981a586fc0403aedb61d54.png) 
Fig. 1: (a) Device and geometrical conventions; (b) Reflection parameter of antenna 1, used to identify the frequencies of the acoustical and optical modes at k=0 (blue lines). (c) and (d)
forward and backward transmission parameters.

technical paper

#### Welcome to the 67th Annual Conference on Magnetism and Magnetic Materials, MMM 2022!

The Conference was held from October 31 to November 4 and offers both in-person and on-demand content.

MMM 2022 is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a tutorial, and several special sessions. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

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The field of magnonics is emerging at blistering pace due to its promising room-temperature applications in logic-based devices at low-power consumption. In view of this,
the exploration of suitable ferromagnetic (FM) La0.67Sr0.33MnO3
(LSMO) and ferroelectric (FE) Pb(Mg0.33Nb0.67)O3-PbTiO3(PMN-PT) magnetoelectric (ME) heterostructures is of
prime interest due to their intimate interface contact [1].
In the present work, a 50-nm-thick LSMO was grown on PMN-PT(001) and PMN-PT(111) single crystals by using pulsed laser deposition. The epitaxial nature of LSMO is confirmed by
x-ray diffraction data. The static and dynamic magnetic response of LSMO/PMN-PT is studied by performing magnetization (M) and ferromagnetic resonance (FMR) measurements. Due
to strong ME coupling at the interface, the LSMO/PMN-PT(001) shows four-fold symmetry of magnetic anisotropy (MA) whereas LSMO/PMN-PT(111) shows isotropic behaviour (see
Fig. 1). The observation can be interpreted on the basis of coupling between the resultant polarisations of PMN-PT and the net M vector of LSMO [2]. To know the effect of ME-induced
MA on the magneto-dynamic response of LSMO, FMR measurements were carried. The FMR data are fitted with the Kittel’s equation and obtained the Gilbert damping constant (α),
which is a key parameter for spin-wave (SW) dynamics, is in the order of 10-2. As the LSMO/PMN-PT(001) is anisotropic in nature, α is found to be smaller along the hard axis than the
easy direction. On the other hand, the LSMO/PMN-PT(111) is isotropic in nature, so that the α remains same in all directions. In order to explore the electric (E-) field effect on the spin
dynamics, FMR data are collected for the LSMO/PMN-PT poled (E = ±10 kV/cm) samples, where a significant reduction in α values is seen. From these combined results, we conclude
that α depends strongly on MA of the films other than its surface roughness, defects, etc. [3]. Although more investigations are required, this particular work hints that it becomes possible
to realize E-field controlled SWs in FM/FEs to develop futuristic magnonic devices. 
**References** 
[1] D. Pesquera, E. Khestanova, M. Ghidini, S. Zhang, A. P. Rooney, F. Maccherozzi, P. Riego, S. Farokhipoor, J. Kim, X. Moya, M. E. Vickers, N. A. Stelmashenko, S. J. 
Haigh, S. S. Dhesi, and N. D. Mathur, Nat. Commun. 11, 3190 (2020). 
[2] G. Venkataiah, Y. Shirahata, M. Itoh, and T. Taniyama, Appl. Phys. Lett. 99, 102506 (2011).
[3] K. Yamada, K. Kogiso, Y. Shiota, M. Yamamoto, A. Yamaguchi, T. Moriyama, T. Ono, and M. Shima, J. Magn. Magn. Mater. 513, 167253 (2020). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/c1bd026c1f887b198288b27847f93dc4.png) 
Fig.1. The polar plots of normalized remanent magnetization (Mr/Ms) of (a) LSMO/PMN-PT(001) and (b) LSMO/PMN-PT(111) heterostructures.

Variation of Gilbert damping constant via interface induced magnetic anisotropy in LSMO/PMN PT heterostructures

Understanding the interaction between magnons and phonons is the key for magnonic applications. In this work, we develop an optical reflectometry to investigate the population of magnons and phonons. Unlike the Brillouin light scattering (BLS) spectroscopy [1, 2], where the sophisticated tandem Fabry-Perot interferometer and single frequency laser with sharp line width are necessary, we use a simple laser-based reflectometry to measure the Kerr rotation and reflectance which are sensitive to the magnon and phonon, respectively.
Using this optical technique, we study the spatial distribution of magnons and phonons in a thulium iron garnet (TmIG) under the temperature gradient generated by current induced Joule
heating. Both the magnon and phonon populations are decaying exponentially as a function of distance from the electrical heating line. We find that the characteristic decay length of the
population of magnons and phonons are different, indicating the non-equilibrium between magnons and phonons in TmIG. Moreover, the characteristic length of magnon population
decreases as increasing the heating power or decreasing the magnetic field, while that of phonon population is almost constant. The different characteristic length of magnon and phonon
population is attributed to the enhanced non-linear magnon scattering processes at high magnon population regime. Our work revealing the magnon-phonon non-equilibrium in TmIG will
motivate the magnonic researches where the role of the magnon-phonon interaction is crucial [3]. 
**References** [1] M. Agrawal., et al., Phys. Rev. Lett. 111, 107204 (2013).
[2] K. An., et al., Phys. Rev. Lett. 117, 107202 (2016).
[3] G.-H. Lee., et al., Appl. Phys. Lett. 119, 152406 (2021).

Probing magnon phonon non

Long-distance transmission of spin angular momentum in antiferromagnetic insulators has attracted much attention [1]. In our previous study, we investigated the spin
transmission in NiO by the enhancement of the damping constant due to the spin pumping effect in NiO tNiO nm/FeNi multilayer films. The results imply that the spin transmission length
could be much greater than 100 nm [2]. In order to accurately determine the transmission length, the structure used in those measurements requires the NiO thickness tNiO >> 100 nm
because the pumped spin current diffuses in the film thickness direction. However, depositing such a thick NiO layer while maintaining the film quality is not practical.In this study, we
devise a structure having the spin transmission in the lateral direction of the NiO layer as shown in Fig. 1 and characterize the damping constant enhancement with respect to the lateral
length lNiO.
Multilayers of NiO 10 nm/FeNi 5 nm/Au 5 nm were fabricated on a single crystalline MgO substrate by magnetron sputtering. The epitaxial growth of the NiO was confirmed by the
RHEED images. We performed the homodyne ferromagnetic resonance measurements for various lNiO. From the lNiO dependence of the damping constant obtained from the measurements, we attempted to derive the in-plane spin transmission length in the NiO. 
**References** 
[1] R. Lebrun et al., Nature 561, 222 (2018)
[2] T. Ikebuchi et al., Appl. Phys. Exp. 14, 123001 (2021) 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/31ebaaf858919615e2be6b378117f25d.png) 
Fig. 1 Schematic illustration of the lateral device and measurement configuration

Characterization of long distance spin transport in antiferromagnetic NiO

In this work, we report the design of a spin torque nano-oscillator (STNO) combined with magnetic flux concentrators (MFCs) to improve the sensitivity of detecting magnetic fields, where the STNO consists of two out-of-plane (OP) ferromagnetic layers separated by a MgO insulating layer (see Fig. 1(a)) and the MFCs placed next to STNO are permalloy. We carried out micromagnetic simulations on the spin-transfer torque (STT) induced magnetic dynamics in the free layer of STNO. Based on the Landau-Lifshitz-Gilbert (LLG)
equation with STT term, the time evolved magnetization precession of the free layer is plotted in Fig. 1(b). First, we show that the ferromagnetic resonance frequency (FMR) of the free
layer magnetization precession can be tuned by the charge current density and external magnetic fields. In addition, the FMR as a function of external magnetic field strength is also studied
on STNO with and without MFCs, see Fig. 1(c). We observed a general suppression of the resonance frequency due to the damping effect of the magnetization induced by MFCs placed at
different distances to the STNO (see Fig. 1(d)). The FMR shift of the STNO free layer magnetization as function of external magnetic field is summarized in Fig 1. (e). By placing MFCs
next to STNO, the lowest detectable magnetic field strength is enhanced from 10 μT to 10 nT. It is concluded that MFCs improve the sensitivity of STNO to external fields due to the
distortion caused by the magnetization damping. The results presented in this work could inspire the optimal design of STNO and MFC-based ultra-low magnetic field sensors. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/300448a262a8a122d2d995834592eccc.png) 
Fig. 1. (a) Schematic view of STNO with a diameter of 80 nm. Charge current is defined as +J and applied in the positive direction. (b) Evolution of the free layer magnetization resonating
in-plane from the initial condition x,y,z> = (0, 0, 1). (c) Schematic view of MFCs placed next to STNO. (d) The distance between MFCs and STNO affects the resonance frequency. J=5e10 A/m2. (e) FMR shift of the magnetization induced by an external magnetic field for an STNO with and without MFCs, where LOD stands for limit of detection. J=5e10 A/m2, MFCs are placed at 70 nm to the STNO.

Magnetic Field Detection Using Spin Torque Nano Oscillator Combined with Magnetic Flux Concentrators

Recent experimental and theoretical work has focused new interest on how magnons can influence the transport properties of metallic ferromagnets (FM). Here we demonstrate the influence the Gilbert damping parameter, αGD, has on both the electron and magnon populations available for transport in two distinctly different CoxFe1-x alloys. The absolute Seebeck coefficient, αabs, is measured for each of the films [1], and we compare to our calculated total thermopower, αtot. To calculate the electronic and magnonic components,
we employ a semi-classical approach; the classical free-electron model estimates the diffusive thermopower component, αMott [2], while we compute the relativistic magnon-drag component, αmd, based on the spin transfer mechanism [3,4]. From these results, we obtain quantitatively comparable measured Seebeck coefficients for both alloys, subsequently showing αmd dominates the low-damping sample, while the alloy with normal damping follows αMott well over our temperature regime. We further present anisotropic magnetoresistance (AMR) [5] and magnetothermopower (MTP) [6] measurements over the temperature range of interest from 125 to 250 K, where we previously reported a significant non-electronic thermal conductivity [7]. AMR measurements align with expected FM metal behavior, while MTP shows a field-dependence as H ∥ ▽T in the low-damping FM metal. We estimate the magnitude of this behavior using the relationship between α(H,⊥) and the inverse resistance, R -1, and calculated the expected α(H,∥) [6]. This argues for an additional field-direction dependent
contribution to thermopower, which could be a novel form of magnon-drag. 
**References** 1. S. J. Mason, A. Hojem, and D. J. Wesenberg, Journ. of Appl. Phys. 127 (2020). 
2. M. Jonson and D. Mahan, Phys. Rev. B 21 (1980). 
3. M. E. Lucassen, C. H. Wong, and R. A. Duine, Appl. Phys. Let. 99 (2011). 
4. B. Flebus, R. A. Duine, and Y. Tserkovnyak, EPL 115 (2016). 
5. J. Shi, S. S. Parkin, and L. Xing, Journ. Of Mag. and Mag. Mater. 125, (1993). 
6. A. D. Avery, M. R. Pufall, and B. L. Zink, Phys. Rev. B – Cond. Mat. and Mater. Phys. 86,(2012). 
7. M. R. Natale, D. J. Wesenberg, and E. R. Edwards, Phys. Rev. Mater. 5, (2021). 
8. M. R. Natale, D. J. Wesenberg, and E. R. Edwards, in preparation 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/cd43a414a645b7b8620c807946139b73.png) 
Fig. 1: Temperature dependence of absolute thermopower for Co25Fe75 alloy. Calculated diffusive, αMott, (green), magnon-drag, αmd, (orange), and total thermopower, αtot, (marron)overlayed with experimental measurements, αmeas
, from 125-250K.

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/769106818bac00aeeb9ad072f65dd768.png) 
Fig. 2: MTP measurement for Co25Fe75 at 200K. αabs(H) is measured in-plane for Hext ⊥ ▽T and Hext ∥ ▽T. Curved arrows indicate the field sweep direction and are color coordinated to distinguish between field-orientation. Dotted lines are expected values.

Magnon drag observed via field

Skyrmions are of great interest in spintronic devices because their small size and the high-speed motion when driven by a current or a spin-wave (SW). Skyrmion motion
along a narrow track is important for racetrack-type spintronic devices, since a skyrmion moving along the propagation direction of an injected electrical or SW current (forward) is the
means by which data are moving[1]. To design the devices, knowing how to adjust the skyrmion motion becomes important.
We carried out simulations of SW driven skyrmion motion using OOMMF [2], with fixed parameters D = 1.5 mJ/m2, MS = 1004 kA/m, A = 3.6 pJ/m, and Ku = 1 MJ/m3. We found that for tracks narrower than 50 nm the skyrmion always moves forwards. For wider tracks, the skyrmion will initially move both backward and close to the track edge, before moving forward at longer times once the track edge is reached, as shown in Fig 1. We attribute this to an additional repulsive force on the skyrmion from the track edge. For samples with Gilbert damping
constant α > 0.06, the skyrmion will move forward without retrograde motion.
The Thiele equation is a widely-used way to analyse skyrmion motion. The SW driving force on a skyrmion is usually the SW scattering force [3], but the strength of the scattering and the
energy change associated with changes in skyrmion size owing to absorbed SWs are hard to extract from magnetization data. Thus, we use the SW transmission T and reflection
coefficients R to make an estimate of the forces involved. We can obtain T from the ratio of the SW amplitude downstream of the skyrmion and without skyrmion at same position.
Similarly, we obtain R from the difference between magnetization data upstream of the skyrmion and without skyrmion.
As an example, we consider the data from a simulation with track width w = 100 nm and α = 0.03. By Analysing T and R, the decrease in T after ~30 ns, shown in Fig.2, will reduce the
effort that leads to the skyrmion moving backward. Meanwhile the increasing force from the sample edge also helps the skyrmion overcome the Spin-Ttansfer Torque between transmitted
SW and skyrmion[4], allowing it to move forwards. 
**References** 
1. Sampaio, J., Cros, V. et al. Nature Nanotech 8, 839–844 (2013) 
2. Donahue, M., Porter D. et al, National Institute of Standards and Technology(1999) 
3. Zhang, X. et al New J. Phys. 19, 065001 (2017) 
4. Yan, X., S. Wang et al. Phys. Rev. Lett. 107, 177207 (2011) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/d19058f8a75b91bfae124e6b897fb99c.png) 
The snapshots of w = 40 nm, 90 nm tracks 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/1486ee39a892911ac9e318a9a335f631.png) 
Time-dependent SW T, R, A and skyrmion acceleration data

Transient retrograde motion of spin wave driven skyrmions in multilayer wave guides

Two-dimensional (2D) intrinsic half-metallic ferromagnets (HMFs) are potential candidates for ultrathin spintronic device applications [1]. The understanding of
magnetocrystalline anisotropy energy (EMCA) and Gilbert damping (α) is required to determine their use in practical applications. In particular, the thermal stability and critical current of
magnetization switching of spin-transfer-torque magnetic random-access memories highly depend on EMCA and α [2]. Therefore, using density functional theory, we study the monolayer
Rhodium dihalides family, RhX2, where X= I, Br, Cl. First, we find that RhX2 prefer 1T phase (octahedral symmetry) than the other possible 1H phase (trigonal prismatic symmetry). The
ferromagnetic ordering is energetically favourable in RhX2 monolayers. The Curie temperature of RhI2, RhBr2 and RhCl2 crystals calculated using spin-wave theory (& Ising model) [3,4]
is 182 (304) K, 92 (189) K and 17 (45) K respectively. We then calculate the spin-polarized electronic band structure which reveals wide intrinsic half-metallic gap (> 1.1 eV) in the down
spin bands of RhX2 monolayers. It results in 100% spin-polarization about the Fermi level and should prevent the spin-current leakage in nanoscale devices. The inclusion of spin-orbit
coupling (SOC) does not affect the band’s profile much and the half-metallic character remains intact. Moreover, the metallic nature arises mainly from the hybridization of Rh 4d-orbitals
and X p-orbitals which are present on the Fermi level. The EMCA and α which originate from SOC control the spin dynamics. We use force theorem [5] for EMCA calculation and the
results show substantial in-plane magnetic anisotropy in RhI2(-2.3 mJ/m2) and RhBr2(-0.57 mJ/m2) whereas small perpendicular anisotropy in RhCl2(0.04 mJ/m2) [6]. To calculate α we employ Kambersky's torque-torque correlation model [7] and it comes out relatively low (2.1×10-2to 4.0×10-3). This work highlights the importance of 2D RhX2 HMFs in fabrication of future spintronic devices. 
**References** 
[1] T. Song, X. Cai and M. W. Y. Tu, Science 360, 1214 (2018). 
[2] S. Ikeda, K. Miura and H. Yamamoto, Nat. Mater. 9, 721 (2010). 
[3] J. L. Lado and J. Fernández-Rossier, 2D Mater. 4, 035002 (2017). 
[4] J. M. Dixon, J. A. Tuszynski and E. J. Carpenter, Physica A 349, 487 (2005). 
[5] D. Li, C. Barreteau, M. R. Castell and F. Silly, Phys. Rev. B 90, 205409 (2014). 
[6] Ram Krishna Ghosh, Ashna Jose and Geetu Kumari, Phys. Rev. B 103, 054409 (2021). 
[7] K. Gilmore, Y. U. Idzerda and M. D. Stiles, Phys. Rev. Lett. 99, 027204 (2007). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/38c5680407b04da4dbeea66d451fd8d3.png) 
Fig.1 a) Side view of 1T-RhX2 monolayer and difference between spin charge densities about Rh and I atoms, b) Electronic band structure of RhI2 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/a967f0757a86ddc2bd90cdd09d0e489b.png) 
Fig.2 a) EMCA vs. θ, b) Gilbert damping tensors vs. life-time broadening.

Magnetocrystalline anisotropy energy and Gilbert damping of two dimensional half

Electrically driven magnetization switch utilizing voltage-controlled magnetic anisotropy (VCMA) have attracted much attention in the new generation memory, especially
for spin-orbit torque (SOT)-based magnetic random access memory (MRAM) [1,2]. For the traditional SOT switching, an additional magnetic field is needed to break the inversion
symmetry, which makes the circuit difficult to implement [3]. Combining the SOT with the VCMA effect can realize the certain switching in SOT-MRAM with lower critical switching
current [4]. With the development of the SOT-MRAM, device model is urgently needed for the device characterization. However, the published models are facing limitations as the size shrinks down
to nanometer. Also, the effect of the elevated temperature caused by repeated operation on the device is non-negligible [5]. Therefore, an effective model is needed to represent the
switching dynamic of the device concerning the influence of the nanoscale and the thermal effect.
In the paper, a compact model of three-terminal VCMA assisted SOT switching is established. The influence of the VCMA effect on the field-free SOT switching is considered by
numerically solving the LLG equations. Furthermore, a 3D model of the VCMA+SOT device is established by finite element method to demonstrate the thermoelectric behavior.
Considering the influence of the thermal effect generated in the working state on the switching characteristics, the electrothermal behavior is integrated into the compact model to show the
influence of the temperature on the switching behavior, highlighting the importance of the thermal effect for the realistic modelling of SOT switching. Additionally, considering the
influence of thermal effect, the switching error rate of the device under different working voltage conditions is evaluated. Finally, a novel voltage pulse scheme is proposed, which can
effectively shorten the inversion time and improve the reliability of the device. The established model provides strategies and guidelines for next-generation memory design and
application. 
**References** [1] W. Kang, Y. Ran and Y. G. Zhang et al., IEEE Trans. Nanotechnol., Vol. 16, p. 387 (2017). 
[2] S. Sharmin, A. Jaiswal, and K. Roy, IEEE Trans. Electron Devices, vol. 63, p. 3493 (2016). 
[3] A. Manchon, I. M. Miron and T. Jungwirth et al., Rev. Mod. Phys., vol. 91, p. 035004 (2019). 
[4] S. Shreya and B. K. Kaushik, IEEE Trans. Electron Devices, vol. 67, p. 90 (2019). 
[5] J. J. Kan, C. Park and C. Ching et al., IEEE Trans. Electron Devices, vol. 64, p. 3639 (2017). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/3ae5dbed55d72a570c2440ec178e1e30.png) 
Fig.1 Schematics of the three-terminal device allowing for field-free SOT switching with an illustration of the influences of VCMA and thermal effects.

Field free switching model of Spin

Spin torque nano oscillator(STNO) and spin Hall nano oscillator(SHNO) are the promising devices to generate spin wave with thermal stability and low power
consumption.
[1,2] But the spin wave has in nature the low power density for device applications. Thus, various spin wave excitation methods have been studied, such as synchronization of
auto-oscillation via multiple SHNO array
[4-7] and utilizing high spin Hall angle in a heavy metal.
[8] Here, we designed a permalloy (Py) ferromagnetic layer in a rectangular bar type for
spin wave excitation by auto oscillation and investigated the effects of a transition metal (Co) alloying on the excitation efficiency. The magnetic fluctuation in bar type layers of Py1-xCox
(x = 0, 0.11, 0.21, 0.29, and 0.40), fabricated by Py-Co cosputtering, is estimated from micro-Brillouin light scattering (μ-BLS) spectroscopy data, as shown in Fig. 1. And the threshold
current for auto oscillation in the bar layers is estimated from the current dependence of integral intensity of the spectra. It is found that Py-Co cosputtering reduces the threshold current for
auto oscillation, e.g., 27.3% for Py1-xCox
(x = 0.21), compared with that of Py layer. It is conjectured that the cosputtering enhances the spin Hall transparency while it causes almost no
change in the effective Gilbert damping constant in the layer. Details will be discussed in the poster presentation and conference proceeding paper. 
**References** 
[1] J. Wunderlich, B. Kaestner, and T. Jungwirth, Phys Rev Lett 94, 047204 (2005). 
[2] J. Torrejon et al., Nature 547, 428 (2017). 
[3] A. Slavin and V. Tiberkevich, IEEE Transactions on Magnetics 45, 1875 (2009). 
[4] Y. Ou, D. C. Ralph, and R. A. Buhrman, Phys Rev Lett 120, 097203 (2018). 
[5] Y. Yin et al., Physical Review B 92 (2015). 
[6] M. A. W. Schoen, D. Thonig, and J. M. Shaw, Nature Physics 12, 839 (2016). 
[7] Y. Fu et al., IEEE Transactions on Magnetics 45, 4004 (2009). 
[8] H. Mazraati et al., Applied Physics Letters 109 (2016). 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/b078253a80d9187c1b90409a52a46000.png) 
Figure 1. Brillouin light scattering (BLS) intensity spectra of Py1-xCox
(x = 0.21) (Py = permalloy) nanowires with various applied DC currents of 3.5, 4.0, 4.5, 5.0 and 5.5 mA

Effects of Permalloy Cobalt Cosputtering in a Nanowire Structure on Magnetic Fluctuation and Auto

Non-reciprocal microwave components such as circulators, isolators, and phase shifters are indispensable tools in both today’s communication systems and future quantum
computers [1-2]. However, these components rely almost entirely on field-based bulky ferrimagnet, which tend to be relatively large, off-chip, and costly to assemble. In this context,
different fields of research are investigating solutions to miniaturize these non-reciprocal devices compatible with integrated circuit technology. Among them, the field of magnonic plays a
key role in this search benefiting from a wide range of non-reciprocal properties in the propagation of spin waves [3]. Recently, unidirectional transmission of spin waves was achieved by
taking advantage of the chiral coupling between the uniform resonance of Co nanowires and exchange spin waves in a thin YIG film [4, 5]. Here, we further miniaturized this method and
demonstrate the possibility of shaping non-reciprocal spin wave beams in a continuous thin YIG film. We performed spin wave spectroscopy on a series of devices made of arrays of Co
bars of dimensions: L=10µm in length, w=200 nm in width, 40nm in thickness, and laterally spaced by a=400nm (see Fig. 1). The transmission spectra done with the external field applied
along the length of the Co bars show perfect non-reciprocity for several peaks located around the resonance frequency of the Co bars, e.g. 8.4 to 10.4 GHz range as shown in Fig. 2. These
peaks correspond to integer values of the lateral spacing between Co bars, e.g. kn=nπ/a ranging up to 80rad/µm. Additional non-reciprocal peaks occurring at lower frequencies ranging
between 2 and 6 GHz correspond to the satellite peaks of the antenna directly coupled to the YIG film. Surprisingly, some of the peaks display a reversed non-reciprocity. Finally, we make
use of this multitude of transmission peaks to characterize the k-dependence of the relaxation time and the group velocity of dipole-exchange spin waves. 
**References** 87.png)[1] W. Palmer, et al., IEEE Micr. Magazine 20, 36 (2019) 
[2] M. Devoret, et al., Superconducting circuits for quantum information,Science 339, 1169 (2013) 
[3] J. Chen, et al., J. Phys. D. Appl. Phys. 55, 123001 (2022) 
[4] H. Wang, et al., Nano Res. 14, 2133–2138 (2021) 
[5] J. Chen, et al., Phys. Rev. B 100, 104427 (2019) 
 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/94e4cd227f20528c8226450f05b99d7c.png) 

SEM image of Co nanowires with length L=10μm, width w=200nm, and period a=400nm lithographed on a 50nm YIG film with thickness, and located under 2 µm wavelength Au coplanar waveguides (CPW)

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/0d51030b4d6ea35e8b9bbc51296dd09e.png) 
Transmission spectrum ΔL21
(blue) and ΔL12
(red) at 24mT applied field.

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Electrical Evidence and Modeling of the Giant Non Reciprocity of Spin

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