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論文

A Large modulation of spin pumping using magnetic phase transitions in single crystalline dysprosium

山野井 一人*; 榊原 有理*; 藤本 純治*; 松尾 衛; 能崎 幸雄*

Applied Physics Express, 16(6), p.063004_1 - 063004_6, 2023/06

We report a large modulation of spin pumping using temperature-induced magnetic phase transitions in c-axis oriented single crystalline dysprosium (Dy). From the temperature variation of the magnetic susceptibility, transitions from paramagnetic (PM) to ferromagnetic (FM) phases via antiferromagnetic (AFM) phase are clearly observed in the Dy. Unlike polycrystalline Dy, the spin pumping of both PM- and AFM-Dy are strongly suppressed owing to the increased non-dissipative backflow of spin current by the long-range spin transport, although two orders of magnitude difference exist between FM- and AFM-phases.

論文

Einstein-de Haas phase shifts in surface acoustic waves

立野 翔真*; 栗宗 勇貴*; 松尾 衛; 山野井 一人*; 能崎 幸雄*

Physical Review B, 104(2), p.L020404_1 - L020404_5, 2021/07

 被引用回数:5 パーセンタイル:58.71(Materials Science, Multidisciplinary)

We demonstrate the phase shift of the Rayleigh-type surface acoustic wave (RSAW) in a ferromagnetic Ni$$_{81}$$Fe$$_{19}$$ film based on the gyromagnetic Einstein-de Haas (EdH) torque that can be attributed to the back action of spin-wave excitation. The EdH torque modulates the transverse velocity of the bulk acoustic wave that causes the bipolar phase shift of RSAW. When compared with a magnetoelastic torque, the phase shift can be more prominently enhanced by increasing the frequency. The gyromagnetic torque in the RSAW paves the way.

論文

Highly nonlinear frequency-dependent spin-wave resonance excited via spin-vorticity coupling

栗宗 勇貴*; 松尾 衛; 前川 禎通; 能崎 幸雄*

Physical Review B, 102(17), p.174413_1 - 174413_7, 2020/11

 被引用回数:15 パーセンタイル:73.8(Materials Science, Multidisciplinary)

A nonuniform vorticity of lattice deformation in a surface acoustic wave (SAW) can generate a spin current (SC) in nonmagnetic metals via spin-vorticity coupling (SVC). We demonstrated a strong enhancement of SVC derived SC generated in Cu and Pt films with increasing the frequency of the SAW by observing the spin-wave resonance (SWR) in an adjacent NiFe film. The comparative amplitudes and high-order frequency variations of SWR in NiFe/Cu and NiFe/Pt bilayers imply that the amplitude of the SC generated via SVC in a SAW is robust against the strength of spin-orbit interaction in nonmagnetic metals.

論文

Electrical evaluation of the alternating spin current generated via spin-vorticity coupling

立野 翔真*; 岡野 元基*; 松尾 衛; 能崎 幸雄*

Physical Review B, 102(10), p.104406_1 - 104406_9, 2020/09

 被引用回数:13 パーセンタイル:69.6(Materials Science, Multidisciplinary)

In many interacting-electron systems, the microscopic spin angular momentum of electrons is conserved along with the macroscopic angular momentum in electrical current flows, i.e., vorticity. Such spin-vorticity coupling expands the choice of materials for spintronics devices. In this paper, we evaluate the magnitude of an alternating spin current generated by the spin-vorticity coupling with a gigahertz-order surface acoustic wave in a Cu thin film. We measure the gigahertz alternating spin current by an electrical method based on the inverse spin-Hall effect. From the amplitude of the spin current, we can determine the conversion efficiency of the angular momentum between local lattice rotation and electron spin in the Cu film. The conversion efficiency is four orders of magnitude larger than the case of spin current generation via kilohertz-order vorticity in turbulent flow of liquid mercury.

論文

Highly accurate evaluation of spin-torque efficiency by measuring in-plane angular dependence of spin-torque ferromagnetic resonance

洞口 泰輔*; 松尾 衛; 能崎 幸雄*

Journal of Magnetism and Magnetic Materials, 505, p.166727_1 - 166727_5, 2020/07

 被引用回数:5 パーセンタイル:43.59(Materials Science, Multidisciplinary)

Spin-torque ferromagnetic resonance (ST-FMR) is a powerful tool to evaluate spin-torque efficiency ($$xi_{rm FMR}$$), the efficiency of current-induced torque in metallic bilayers consisting of ferromagnetic and nonmagnetic materials. In general, $$xi_{rm FMR}$$ can be evaluated from the amplitude ratio between symmetric and anti-symmetric components of the ST-FMR spectrum. However, the ratio is also affected by an unnecessary magnetic field owing to the asymmetric alternating current flow used to excite the ST-FMR. In this article, we demonstrate that $$xi_{rm FMR}$$ can be precisely evaluated from the full-angular dependence of the ST-FMR spectrum even though the distribution of alternating current flow is highly asymmetric.

論文

Observation of gyromagnetic spin wave resonance in NiFe films

栗宗 勇貴*; 松尾 衛; 能崎 幸雄*

Physical Review Letters, 124(21), p.217205_1 - 217205_6, 2020/05

 被引用回数:27 パーセンタイル:89.26(Physics, Multidisciplinary)

強磁性薄膜における表面弾性波による磁気ジャイロ効果由来のスピン波共鳴に関して報告する。NiFe薄膜における磁気ジャイロ効果由来のスピン波共鳴の強度はNi薄膜における磁歪由来のものより高調波成分をふくむ。この周波数依存性は表面弾性波によって生じる格子の局所的回転運動により理解できる。スピン波共鳴の周波数依存性から磁歪によるスピン波共鳴を分離することが可能である。

論文

Spin current generation using a surface acoustic wave generated via spin-rotation coupling

小林 大眞*; 吉川 智英*; 松尾 衛*; 井口 亮*; 前川 禎通; 齊藤 英治; 能崎 幸雄*

Physical Review Letters, 119(7), p.077202_1 - 077202_5, 2017/08

 被引用回数:104 パーセンタイル:97.38(Physics, Multidisciplinary)

We demonstrate the generation of alternating spin current (SC) via spin-rotation coupling (SRC) using a surface acoustic wave (SAW) in a Cu film. Ferromagnetic resonance caused by injecting SAWs was observed in a Ni-Fe film attached to a Cu film, with the resonance further found to be suppressed through the insertion of a SiO$$_{2}$$ film into the interface. The intensity of the resonance depended on the angle between the wave vector of the SAW and the magnetization of the Ni-Fe film. This angular dependence is explicable in terms of the presence of spin transfer torque from a SC generated via SRC.

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