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Giant spin hydrodynamic generation in laminar flow

高橋 遼*; 中堂 博之; 松尾 衛; 針井 一哉*; 大沼 悠一*; 前川 禎通; 齊藤 英治

Nature Communications (Internet), 11, p.3009_1 - 3009_6, 2020/06

 被引用回数:0 パーセンタイル:100(Multidisciplinary Sciences)

Hydrodynamic motion can generate a flux of electron-spin's angular momentum via the coupling between fluid rotation and electron spins. Such hydrodynamic generation, called spin hydrodynamic generation (SHDG), has recently attracted attention in a wide range of fields, especially in spintronics. Spintronics deals with spin-mediated interconversion taking place on a micro or nano scale because of the spin-diffusion length scale. To be fully incorporated into the interconversion, SHDG physics should also be established in such a minute scale, where most fluids exhibit a laminar flow. Here, we report electric voltage generation due to the SHDG in a laminar flow of a liquid-metal mercury. The experimental results show a scaling rule unique to the laminar-flow SHDG. Furthermore, its energy con- version efficiency turns out to be about 105 greater than of the turbulent one. Our findings reveal that the laminar-flow SHDG is suitable to downsizing and to extend the coverage of fluid spintronics.


Universal $$frac{1}{3}$$-suppression of magnonic shot noise in diffusive insulating magnets

仲田 光樹; 大沼 悠一*; 松尾 衛*

Physical Review B, 100(1), p.014406_1 - 014406_8, 2019/07

 被引用回数:0 パーセンタイル:100(Materials Science, Multidisciplinary)



Angular momentum compensation manipulation to room temperature of the ferrimagnet Ho$$_{3-x}$$Dy$$_{x}$$Fe$$_5$$O$$_{12}$$ detected by the Barnett effect

今井 正樹; 中堂 博之; 小野 正雄; 針井 一哉; 松尾 衛; 大沼 悠一*; 前川 禎通; 齊藤 英治

Applied Physics Letters, 114(16), p.162402_1 - 162402_4, 2019/04

 被引用回数:7 パーセンタイル:21.51(Physics, Applied)

We demonstrate that the angular momentum compensation temperature $$T_{rm A}$$, at which the net angular momentum in the sample disappears, can be controlled in Ho$$_3$$Fe$$_5$$O$$_{12}$$ by partially substituting Dy for Ho. The $$T_{rm A}$$ can be detected using the Barnett effect, by which mechanical rotation magnetizes an object due to spin-rotation coupling. We found that $$T_{rm A}$$ increases with the Dy content and clarified that the $$T_{rm A}$$ of Ho$$_{1.5}$$Dy$$_{1.5}$$Fe$$_5$$O$$_{12}$$ coincides with room temperature. The Barnett effect enables us to explore materials applicable to magnetic devices utilizing the angular momentum compensation only by rotating the powder sample at room temperature.


Asymmetric quantum shot noise in magnon transport

仲田 光樹; 大沼 悠一*; 松尾 衛*

Physical Review B, 99(13), p.134403_1 - 134403_7, 2019/04

 被引用回数:2 パーセンタイル:56.85(Materials Science, Multidisciplinary)




川俣 貴則; 小沼 勇一; 花川 裕規

JAEA-Review 2018-031, 33 Pages, 2019/02


平成29年度に「原子力災害対策特別保護法に基づき原子力防災管理者が通報すべき事象等に関する規則」の改正・施行に伴い、大洗研究所の原子力事業者防災業務計画の見直しが原子力規制庁から指示された。そのため、JMTRにおいても緊急時活動レベル(Emergency Action Level(以下、EALという。))の作成が新たに必要となった。JMTRのような試験研究炉は、その特性が多岐にわっている。そのため、JMTRの特性と発電用原子炉施設のEALを踏まえた上で、JMTRにおけるEALを設定する必要があった。本報告では、JMTRにおけるEAL設定の基本方針及び選定結果について報告する。



佐々木 宏和*; 西久保 英郎*; 西田 真輔*; 山崎 悟志*; 中崎 竜介*; 磯松 岳己*; 湊 龍一郎*; 衣川 耕平*; 今村 明博*; 大友 晋哉*; et al.

古河電工時報, (138), p.2 - 10, 2019/02



Magnonic noise and Wiedemann-Franz law

仲田 光樹; 大沼 悠一*; 松尾 衛*

Physical Review B, 98(9), p.094430_1 - 094430_8, 2018/09

 被引用回数:8 パーセンタイル:32.09(Materials Science, Multidisciplinary)



Observation of gyromagnetic reversal

今井 正樹; 緒方 裕大*; 中堂 博之; 小野 正雄; 針井 一哉; 松尾 衛*; 大沼 悠一*; 前川 禎通; 齊藤 英治

Applied Physics Letters, 113(5), p.052402_1 - 052402_3, 2018/07

 被引用回数:9 パーセンタイル:36.37(Physics, Applied)

We report direct observation of gyromagnetic reversal, which is the sign change of gyromagnetic ratio in a ferrimagnet Ho$$_3$$Fe$$_5$$O$$_{12}$$, by using the Barnett effect measurement technique at low temperatures. The Barnett effect is a phenomenon in which magnetization is induced by mechanical rotation through the coupling between rotation and total angular momentum $$J$$ of electrons. The magnetization of Ho$$_3$$Fe$$_5$$O$$_{12}$$ induced by mechanical rotation disappears at 135 K and 240 K. The temperatures correspond to the magnetization compensation temperature $$T_{rm M}$$ and the angular momentum compensation temperature $$T_{rm A}$$, respectively. Between $$T_{rm M}$$ and $$T_{rm A}$$, the magnetization flips over to be parallel against the angular momentum due to the sign change of gyromagnetic ratio. This study provides an unprecedented technique to explore the gyromagnetic properties.


Dirac surface state-modulated spin dynamics in a ferrimagnetic insulator at room temperature

Tang, C.*; Song, Q.*; Chang, C.-Z.*; Xu, Y.*; 大沼 悠一; 松尾 衛*; Liu, Y.*; Yuan, W.*; Yao, Y.*; Moodera, J. S.*; et al.

Science Advances (Internet), 4(6), p.eaas8660_1 - eaas8660_6, 2018/06

 被引用回数:8 パーセンタイル:26.78(Multidisciplinary Sciences)

This work demonstrates markedly modified spin dynamics of magnetic insulator (MI) by the spin momentum-locked Dirac surface states of the adjacent topological insulator (TI). As the Bi concentration $$x$$ is systematically tuned in 5-nm-thick (Bi$$_{x}$$Sb$$_{1-x}$$)$$_{2}$$Te$$_{3}$$ TI films, the weight of the surface relative to bulk states peaks at $$x$$ = 0.32 when the chemical potential approaches the Dirac point. At this concentration, the Gilbert damping constant of the precessing magnetization in 10-nm-thick Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$ MI films in the MI/TI heterostructures is enhanced by an order of magnitude, the largest among all concentrations. In addition, the MI acquires additional strong magnetic anisotropy that favors the in-plane orientation with similar Bi concentration dependence. These extraordinary effects of the Dirac surface states distinguish TI from other materials such as heavy metals in modulating spin dynamics of the neighboring magnetic layer.


Spin current noise of the spin Seebeck effect and spin pumping

松尾 衛*; 大沼 悠一; 加藤 岳生*; 前川 禎通

Physical Review Letters, 120(3), p.037201_1 - 037201_5, 2018/01

 被引用回数:19 パーセンタイル:9.11(Physics, Multidisciplinary)




大沼 悠一; 松尾 衛*; 前川 禎通; 齊藤 英治

まぐね, 12(5), p.217 - 224, 2017/10



Theory of the spin Peltier effect

大沼 悠一; 松尾 衛*; 前川 禎通

Physical Review B, 96(13), p.134412_1 - 134412_4, 2017/10

 被引用回数:21 パーセンタイル:14.69(Materials Science, Multidisciplinary)



Theory of spin hydrodynamic generation

松尾 衛*; 大沼 悠一; 前川 禎通

Physical Review B, 96(2), p.020401_1 - 020401_5, 2017/07

 被引用回数:14 パーセンタイル:25.88(Materials Science, Multidisciplinary)



Spin transport in half-metallic ferromagnets

大沼 悠一; 松尾 衛; 前川 禎通

Physical Review B, 94(18), p.184405_1 - 184405_5, 2016/11

 被引用回数:9 パーセンタイル:43.52(Materials Science, Multidisciplinary)



Origin of the spin Seebeck effect in compensated ferrimagnets

Gepr$"a$gs, S.*; Kehlberger, A.*; Coletta, F.*; Qiu, Z.*; Guo, E.-J.*; Schulz, T.*; Mix, C.*; Meyer, S.*; Kamra, A.*; Althammer, M.*; et al.

Nature Communications (Internet), 7, p.10452_1 - 10452_6, 2016/02

 被引用回数:80 パーセンタイル:2.93(Multidisciplinary Sciences)

Magnons are the elementary excitations of a magnetically ordered system. Here, we show that the spin Seebeck effect is sensitive to the complexities of the magnon spectrum. The spin Seebeck effect is caused by a thermally excited spin dynamics that is converted to a voltage by the inverse spin Hall effect at the interface to a heavy metal contact. By investigating the temperature dependence of the spin Seebeck effect in the ferrimagnet gadlinium iron garnet, with a magnetic compensation point near room temperature, we demonstrate that high-energy exchange magnons play a key role in the spin Seebeck effect.


Magnon instability driven by heat current in magnetic bilayers

大沼 悠一*; 安立 裕人; 齊藤 英治; 前川 禎通

Physical Review B, 92(22), p.224404_1 - 224404_8, 2015/12

 被引用回数:7 パーセンタイル:58.13(Materials Science, Multidisciplinary)

We theoretically demonstrate that in a ferromagnet/paramagnet bilayer, a magnon instability accompanied by a gigahertz microwave emission can be driven simply by means of a temperature bias. Employing many-body theory for investigating the effects of a phonon heat current on the magnon lifetime, we show that the magnon instability occurs upon the suppression of the umklapp scattering at low temperatures, leading to microwave emission. The present finding provides crucial information about the interplay of spin current and heat current.


Enhanced dc spin pumping into a fluctuating ferromagnet near Tc

大沼 悠一*; 安立 裕人; 齊藤 英治; 前川 禎通

Physical Review B, 89(17), p.174417_1 - 174417_10, 2014/05

 被引用回数:61 パーセンタイル:6.75(Materials Science, Multidisciplinary)

A linear-response formulation of the dc spin pumping, i.e., a spin injection from a precessing ferromagnet into an adjacent spin sink, is developed in view of describing many-body effects caused by spin fluctuations in the spin sink. It is shown that, when an itinerant ferromagnet near Tc is used as the spin sink, the spin pumping is largely increased owing to the fluctuation enhancement of the spin conductance across the precessing ferromagnet/spin sink inerface. As an example, the enhanced spin pumping from yttrium iron garnet into nickel palladium alloy is analyzed by means of a self-consistent renormalization scheme, and it is predicted that the enhancement can be as large as tenfold.


Simulator for materials testing reactors

竹本 紀之; 菅谷 直人; 大塚 薫; 花川 裕規; 小沼 勇一; 細川 甚作; 堀 直彦; 神永 雅紀; 田村 一雄*; 堀田 浩司*; et al.

JAEA-Technology 2013-013, 44 Pages, 2013/06




Spin Seebeck effect in antiferromagnets and compensated ferrimagnets

大沼 悠一; 安立 裕人; 齊藤 英治; 前川 禎通

Physical Review B, 87(1), p.014423_1 - 014423_7, 2013/01

 被引用回数:86 パーセンタイル:4.03(Materials Science, Multidisciplinary)

We theoretically investigate the spin Seebeck effect (SSE) in antiferromagnets and ferrimagnets, and show that the SSE vanishes in antiferromagnets but survives in ferrimagnets even at the magnetization compensation point despite the absence of its saturation magnetization. The nonvanishing SSE in ferrimagnets stems from two nondegenerate magnons. We demonstrate that the magnitude of the SSE in ferrimagnets is unchanged across the magnetization compensation point.



高橋 澄; 塙 博; 小沼 勇一; 細川 甚作; 菅野 勝

JAEA-Technology 2012-007, 31 Pages, 2012/03



46 件中 1件目~20件目を表示