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Lyons, T. P.*; Puebla, J.*; 山本 慧; Deacon, R. S.*; Hwang, Y.*; 石橋 幸治*; 前川 禎通*; 大谷 義近*
Physical Review Letters, 131(19), p.196701_1 - 196701_6, 2023/11
被引用回数：0Harnessing the causal relationships between mechanical and magnetic properties of van der Waals materials presents a wealth of untapped opportunity for scientific and technological advancement, from precision sensing to novel memories. This can, however, only be exploited if the means exist to efficiently interface with the magnetoelastic interaction. Here, we demonstrate acoustically-driven spin-wave resonance in a crystalline antiferromagnet, chromium trichloride, via surface acoustic wave irradiation. The resulting magnon-phonon coupling is found to depend strongly on sample temperature and external magnetic field orientation, and displays a high sensitivity to extremely weak magnetic anisotropy fields in the few mT range. Our work demonstrates a natural pairing between power-efficient strain-wave technology and the excellent mechanical properties of van der Waals materials, representing a foothold towards widespread future adoption of dynamic magneto-acoustics.
Liao, L.*; Puebla, J.*; 山本 慧; Kim, J.*; 前川 禎通*; Hwang, Y.*; Ba, Y.*; 大谷 義近*
Physical Review Letters, 131(17), p.176701_1 - 176701_6, 2023/10
被引用回数：0Phonons and magnons are engineered by periodic potential landscapes in phononic and magnonic crystals, and their combined studies may enable valley phonon transport tunable by the magnetic field. Through nonreciprocal surface acoustic wave transmission, we demonstrate valley-selective phonon-magnon scattering in magnetoelastic superlattices. The lattice symmetry and the out-of-plane magnetization component control the sign of nonreciprocity. The phonons in the valleys play a crucial role in generating nonreciprocal transmission by inducing helical strains that couple with the magnons. The transmission spectra show a nonreciprocity peak near a transmission gap, matching the phononic band structure. Our results open the way for manipulating valley phonon transport through periodically varying magnon-phonon coupling.
Puebla, J.*; Hwang, Y.*; 前川 禎通*; 大谷 義近*
Applied Physics Letters, 120(22), p.220502_1 - 220502_9, 2022/05
被引用回数：18 パーセンタイル：92.05(Physics, Applied)Surface acoustic waves (SAWs) are elastic waves propagating on the surface of solids with the amplitude decaying into the solid. The well- established fabrication of compact SAW devices, together with well-defined resonance frequencies, places SAWs as an attractive route to manipulate the magnetization states in spintronics, all of which is made possible by the magnetostriction and magnetoelastic effects. Here, we review the basic characteristics of SAW devices and their interaction out-of-resonance and in-resonance with the magnetization in thin films. We describe our own recent results in this research field and closely related works and provide our perspectives moving forward.
山本 慧; Xu, M.*; Puebla, J.*; 大谷 義近*; 前川 禎通*
Journal of Magnetism and Magnetic Materials, 545, p.168672_1 - 168672_10, 2022/03
被引用回数：10 パーセンタイル：52.49(Materials Science, Multidisciplinary)We present a theoretical description of magnon-phonon interactions in a multi-layer structure containing a ferromagnetic thin film. The formalism is applicable to an arbitrary direction of external magnetic field and various types of acoustic waves including Rayleigh and Love surface modes. A particular attention is paid to the spatial profile of the acoustic wave modes and analytical expressions for the effective coupling coefficients are derived taking into account the degree of mode profile overlap between spin waves and acoustic waves. The results are applied to reproduce a strongly anisotropic and non-reciprocal linewidth of acoustic ferromagnetic resonance reported in a recent experiment.
山本 慧; Yu, W.*; Yu, T.*; Puebla, J.*; Xu, M.*; 前川 禎通*; Bauer, G.*
Journal of the Physical Society of Japan, 89(11), p.113702_1 - 113702_5, 2020/11
被引用回数：10 パーセンタイル：62.22(Physics, Multidisciplinary)We predict that surface acoustic waves are generated preferentially in one direction in a heterostructure of a thin magnetic film on a non-magnetic substrate. The non-reciprocity arises from magneto-elastic coupling and magneto-rotation coupling, the former being dominant for YIG/GGG heterostructures. For YIG films thinner than about 100 nm, the surface acoustic wave amplitude is nearly unidirectional at certain angles of the in-plane equilibrium magnetisation. We compute the full magnetic field dependence of the effect for a selected device.
Xu, M.*; 山本 慧; Puebla, J.*; Baumgaertl, K.*; Rana, B.*; 三浦 勝哉*; 高橋 宏昌*; Grundler, D.*; 前川 禎通*; 大谷 義近*
Science Advances (Internet), 6(32), p.eabb1724_1 - eabb1724_4, 2020/08
被引用回数：81 パーセンタイル：97.1(Multidisciplinary Sciences)One of the most fundamental forms of magnon-phonon-interaction is an intrinsic property of magnetic materials, the "magnetoelastic coupling." This particular form of interaction has been the basis for describing magnetic materials and their strain related applications, where strain induces changes of internal magnetic fields. Different from the magnetoelastic coupling, more than 40 years ago, it was proposed that surface acoustic waves may induce surface magnons via rotational motion of the lattice in anisotropic magnets. However, a signature of this magnon-phonon coupling mechanism, termed magneto-rotation coupling, has been elusive. Here, we report the first observation and theoretical framework of the magneto-rotation coupling in a perpendicular anisotropic ultra-thin lim Ta/CoFeB/MgO, which consequently induces nonreciprocal acoustic wave attenuation with an unprecedented ratio up to 100% rectification at a theoretically predicted optimized condition. Our work not only experimentally demonstrates a fundamentally new path for investigating magnon-phonon coupling, but also justifies the feasibility of the magneto-rotation coupling based application.
Puebla, J.*; Xu, M.*; Rana, B.*; 山本 慧; 前川 禎通*; 大谷 義近*
Journal of Physics D; Applied Physics, 53(26), p.264002_1 - 264002_7, 2020/06
被引用回数：31 パーセンタイル：87.05(Physics, Applied)Voltage induced magnetization dynamics of magnetic thin films is a valuable tool to study anisotropic fields, exchange couplings, magnetization damping and spin pumping mechanism. A particularly well established technique is the ferromagnetic resonance (FMR) generated by the coupling of microwave photons and magneti- zation eigenmodes in the GHz range. Here we review the basic concepts of the so-called acoustic ferromagnetic resonance technique (a-FMR) induced by the coupling of surface acoustic waves (SAW) and magnetization of thin films. Interestingly, additional to the benefits of the microwave excited FMR technique, the coupling be- tween SAW and magnetization also offers fertile ground to study magnon-phonon and spin rotation couplings. We describe the in-plane magnetic field angle dependence of the a-FMR by measuring the absorption / trans- mission of SAW and the attenuation of SAW in the presence of rotational motion of the lattice, and show the consequent generation of spin current by acoustic spin pumping.
山本 慧; Yu, W.*; Xu, M.*; Puebla, J.*; 前川 禎通*; Bauer, G.*
no journal, ,
本研究発表では、表面音波透過率における非相反性の逆効果である、スピン波を外部マイクロ波磁場で励起することによる表面音波の一方向への選択的励起を理論的に提案する。この効果は表面音波に伴う力学的回転とスピン波歳差運動の間の通常の磁気弾性結合および磁気回転結合を介したカイラル相互作用にのみ依存しており、特別な微細加工を必要としない。磁場を印加した領域から左右に向かって広がる音波の振幅の大きさの差は磁化の方向と磁石の膜厚に依存する。磁性絶縁体Y
Fe
O
においては50nm程度の膜厚が非相反性を最大化し、磁化と音波の伝搬方向の間の角度がおよそ15度の時、表面音波は一方向にのみ発生することを解析的計算により示す。
