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Chen, J.*; 山本 慧; Zhang, J.*; Ma, J.*; Wang, H.*; Sun, Y.*; Chen, M.*; Ma, J.*; Liu, S.*; Gao, P.*; et al.
Physical Review Applied (Internet), 19(2), p.024046_1 - 024046_9, 2023/02
被引用回数：6 パーセンタイル：90.23(Physics, Applied)Coherent coupling in magnon based hybrid system has many potential applications in quantum information processing. Magnons can propagate in magnetically ordered materials without any motion of electrons, offering a unique method to build low-power-consumption devices and information channels free of heat dissipation. In this article, we demonstrate the coherent propagation of hybridized modes between spin waves and Love surface acoustic waves in a multiferroic BiFeO
and ferromagnetic La
Sr
MnO based heterostructure. The magneto-elastic coupling enables a giant enhancement of strength of the hybridized mode by a factor of 26 compared to that of the pure spin waves. A short wavelength down to 250 nm is demonstrated for the hybridized mode, which is desirable for nanoscale acousto-magnonic applications. Our combined experimental and theoretical analyses represent an important step towards the coherent control in hybrid magnonics, which may inspire the study of magnon-phonon hybrid systems for coherent information processing and manipulation.
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：13 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：88 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：33 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YFe
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。
山本 慧
no journal, ,
レイリー表面音波は様々な弾性体の表面を普遍的に伝搬し、圧力センサー等への工学応用が進んでいるが、他方でその制御性の高さから物性測定のツールとしても幅広く利用されてきた。本講演では、磁性体の薄膜とレイリー表面音波の相互作用によって生じるスピン波共鳴を用いたスピンダイナミクスに関する研究について紹介する。通常スピン波の波数分解測定にはレーザー光などの電磁波をプローブとして用いるが、同じ波長において電磁波はスピン波に比して桁違いに高い周波数を持つため共鳴的な測定を行うことは出来ない。表面音波をプローブとして使うことでマイクロ波周波数において音波とスピン波の共鳴現象が生じ、微弱な相互作用から巨大な信号を得ることが可能になる。この増幅効果によって磁性体中のスピン間相互作用を精度良く測定できることを解説する。またレイリー表面音波が界面における反転対称性の欠如に起因する特徴的な力学的回転運動を伴っていることに着目した最近の研究成果に触れ、電子スピンと力学的回転運動の結合を調べる可能性について議論する。
