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Journal Articles

Enhancement of domain-wall mobility detected by NMR at the angular momentum compensation temperature

Imai, Masaki; Chudo, Hiroyuki; Matsuo, Mamoru; Maekawa, Sadamichi; Saito, Eiji

Physical Review B, 102(1), p.014407_1 - 014407_5, 2020/07

 Times Cited Count:1 Percentile:100(Materials Science, Multidisciplinary)

Journal Articles

Giant spin hydrodynamic generation in laminar flow

Takahashi, Ryo*; Chudo, Hiroyuki; Matsuo, Mamoru; Harii, Kazuya*; Onuma, Yuichi*; Maekawa, Sadamichi; Saito, Eiji

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

 Times Cited Count:0 Percentile:100(Multidisciplinary Sciences)

Journal Articles

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

Nakata, Koki; Onuma, Yuichi*; Matsuo, Mamoru*

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

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

Extending a Boltzmann-Langevin theory to magnons, we show a universality of current-noise suppression in diffusive systems against the difference of quantum-statistical properties of bosons and fermions.

Journal Articles

Spin Seebeck mechanical force

Harii, Kazuya; Seo, Y.-J.*; Tsutsumi, Yasumasa*; Chudo, Hiroyuki; Oyanagi, Koichi*; Matsuo, Mamoru; Shiomi, Yuki*; Ono, Takahito*; Maekawa, Sadamichi; Saito, Eiji

Nature Communications (Internet), 10(1), p.2616_1 - 2616_5, 2019/06

 Times Cited Count:10 Percentile:11.06(Multidisciplinary Sciences)

Journal Articles

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

Imai, Masaki; Chudo, Hiroyuki; Ono, Masao; Harii, Kazuya; Matsuo, Mamoru; Onuma, Yuichi*; Maekawa, Sadamichi; Saito, Eiji

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

 Times Cited Count:7 Percentile:21.51(Physics, Applied)

Journal Articles

Asymmetric quantum shot noise in magnon transport

Nakata, Koki; Onuma, Yuichi*; Matsuo, Mamoru*

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

 Times Cited Count:2 Percentile:56.85(Materials Science, Multidisciplinary)

We study a frequency-dependent noise-to-current ratio for asymmetric, symmetric, and noncommutative current noise in a ferromagnetic insulating junction, and extract quantum-mechanical properties of magnon transport at low temperatures. We demonstrate that the noncommutative noise, which vanishes in the dc limit (i.e., a classical regime), increases monotonically as a function of frequency, and show that the noncommutative noise associated directly with quantum fluctuations of magnon currents breaks through the classical upper limit determined by the symmetric noise and realizes asymmetric quantum shot noise. Finally, we show that our theoretical predictions are within experimental reach with current device and measurement schemes while exploiting low temperatures. Our work provides a platform toward experimental access to quantum fluctuations of magnon currents.

Journal Articles

Magnonic noise and Wiedemann-Franz law

Nakata, Koki; Onuma, Yuichi*; Matsuo, Mamoru*

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

 Times Cited Count:8 Percentile:32.09(Materials Science, Multidisciplinary)

We theoretically establish mutual relations among magnetic momentum, heat, and fluctuations of propagating magnons in a ferromagnetic insulating junction in terms of noise and the bosonic Wiedemann-Franz (WF) law. Using the Schwinger-Keldysh formalism, we calculate all transport coefficients of a noise spectrum for both magnonic spin and heat currents, and establish Onsager relations between the thermomagnetic currents and the zero-frequency noise. Making use of the magnonic WF law and the Seebeck coefficient in the low-temperature limit, we theoretically discover universal relations, i.e. being independent of material parameters, for both the nonequilibrium and equilibrium noise, and show that each noise is described solely in terms of thermal conductance.

Journal Articles

Observation of gyromagnetic reversal

Imai, Masaki; Ogata, Yudai*; Chudo, Hiroyuki; Ono, Masao; Harii, Kazuya; Matsuo, Mamoru*; Onuma, Yuichi*; Maekawa, Sadamichi; Saito, Eiji

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

 Times Cited Count:9 Percentile:36.37(Physics, Applied)

Journal Articles

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

Tang, C.*; Song, Q.*; Chang, C.-Z.*; Xu, Y.*; Onuma, Yuichi; Matsuo, Mamoru*; Liu, Y.*; Yuan, W.*; Yao, Y.*; Moodera, J. S.*; et al.

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

 Times Cited Count:8 Percentile:26.78(Multidisciplinary Sciences)

Journal Articles

Spin current noise of the spin Seebeck effect and spin pumping

Matsuo, Mamoru*; Onuma, Yuichi; Kato, Takeo*; Maekawa, Sadamichi

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

 Times Cited Count:19 Percentile:9.11(Physics, Multidisciplinary)

We theoretically investigate the fluctuation of a pure spin current induced by the spin Seebeck effect and spin pumping in a normal metal (NM)/ferromagnet (FM) bilayer system. Starting with a simple FI-NM interface model with both spin-conserving and spin-non-conserving processes, we derive general expressions of the spin current and the spin-current noise at the interface within second-order perturbation of the FI-NM coupling strength, and estimate them for an yttrium iron garnet (YIG) - platinum interface. We show that the spin-current noise can be used to determine the effective spin carried by a magnon modified by the spin-non-conserving process at the interface. In addition, we show that it provides information on the effective spin of a magnon, heating at the interface under spin pumping, and spin Hall angle of the NM.

Journal Articles

Enhanced orbital magnetic moment in FeCo nanogranules observed by Barnett effect

Ogata, Yudai; Chudo, Hiroyuki; Gu, B.; Kobayashi, Nobukiyo*; Ono, Masao; Harii, Kazuya; Matsuo, Mamoru; Saito, Eiji; Maekawa, Sadamichi

Journal of Magnetism and Magnetic Materials, 442, p.329 - 331, 2017/11

 Times Cited Count:4 Percentile:49.06(Materials Science, Multidisciplinary)

Journal Articles

Heat and spin interconversion

Onuma, Yuichi; Matsuo, Mamoru*; Maekawa, Sadamichi; Saito, Eiji

Magune, 12(5), p.217 - 224, 2017/10

no abstracts in English

Journal Articles

Theory of the spin Peltier effect

Onuma, Yuichi; Matsuo, Mamoru*; Maekawa, Sadamichi

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

 Times Cited Count:21 Percentile:14.69(Materials Science, Multidisciplinary)

A microscopic theory of the spin Peltier effect in a bilayer structure comprising a paramagnetic metal (PM) and a ferromagnetic insulator (FI) based on the nonequilibrium Green's function method is presented. Spin current and heat current driven by temperature gradient and spin accumulation are formulated as functions of spin susceptibilities in the PM and the FI, and are summarized by Onsager's reciprocal relations. By using the current formulas, we estimate heat generation and absorption at the interface driven by the heat-current injection mediated by spins from PM into FI.

Journal Articles

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

Kobayashi, Daima*; Yoshikawa, Tomohide*; Matsuo, Mamoru*; Iguchi, Ryo*; Maekawa, Sadamichi; Saito, Eiji; Nozaki, Yukio*

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

 Times Cited Count:36 Percentile:5.76(Physics, Multidisciplinary)

Journal Articles

Theory of spin hydrodynamic generation

Matsuo, Mamoru*; Onuma, Yuichi; Maekawa, Sadamichi

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

 Times Cited Count:14 Percentile:25.88(Materials Science, Multidisciplinary)

Spin-current generation by fluid motion is theoretically investigated. Based on quantum kinetic theory, the spin-diffusion equation coupled with fluid vorticity is derived. We show that spin currents are generated by the vorticity gradient in both laminar and turbulent flows and that the generated spin currents can be detected by the inverse spin Hall voltage measurements, which are predicted to be proportional to the flow velocity in a laminar flow. In contrast, the voltage in a turbulent flow is proportional to the square of the flow velocity. This study will pave the way to fluid spintronics.

Journal Articles

Gyroscopic $$g$$ factor of rare earth metals

Ogata, Yudai; Chudo, Hiroyuki; Ono, Masao; Harii, Kazuya; Matsuo, Mamoru; Maekawa, Sadamichi; Saito, Eiji

Applied Physics Letters, 110(7), p.072409_1 - 072409_4, 2017/02

 Times Cited Count:9 Percentile:37.35(Physics, Applied)

Journal Articles


Matsuo, Mamoru; Saito, Eiji; Maekawa, Sadamichi

Journal of the Physical Society of Japan, 86(1), p.011011_1 - 011011_7, 2017/01

 Times Cited Count:11 Percentile:24.69(Physics, Multidisciplinary)

We investigate the interconversion phenomena between spin and mechanical angular momentum in moving objects. In particular, the recent results on spin manipulation and spin-current generation by mechanical motion are examined. In accelerating systems, spin-dependent gauge fields emerge, which enable the conversion from mechanical angular momentum into spins. Such a spin-mechanical effect is predicted by quantum theory in a non-inertial frame. Experiments which confirm the effect, i.e., the resonance frequency shift in nuclear magnetic resonance, the stray field measurement of rotating metals, and electric voltage generation in liquid metals, are discussed.

Journal Articles

Spin hydrodynamic generation

Matsuo, Mamoru

Oyo Butsuri, 86(1), p.31 - 35, 2017/01

Spin-current generation by fluid motion is investigated. Spin-rotation coupling emerges in a rotating object and allows the angular momentum conversion from mechanical angular momentum into spins. We predicted that the spin current is mechanically generated along the vorticity gradient of the liquid metal pipe flow. Such spin-mechanical effect is experimentally confirmed by electric voltage generation in liquid metals. The use of the interconversion between spin and mechanical angular momentum opens up a new field of spintronics, where spin and mechanical motion are harmonized.

Journal Articles

Spin transport in half-metallic ferromagnets

Onuma, Yuichi; Matsuo, Mamoru; Maekawa, Sadamichi

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

 Times Cited Count:9 Percentile:43.52(Materials Science, Multidisciplinary)

We theoretically investigate spin transport in half-metallic ferromagnets at finite temperatures. The side-jump and skew-scattering contributions to spin Hall conductivity are derived using the Kubo formula. The electron-magnon interaction causes a finite density of states in the energy gap of the minority-spin band and induces spin Hall conductivity. We show that spin Hall conductivity is proportional to $$T^{3/2}$$, with $$T$$ being temperature and is sensitive to $$T$$. We propose that spin Hall conductivity may be a tool to study the minority-spin state.

Journal Articles

Spin hydrodynamic generation

Takahashi, Ryo*; Matsuo, Mamoru; Ono, Masao; Harii, Kazuya; Chudo, Hiroyuki; Okayasu, Satoru; Ieda, Junichi; Takahashi, Saburo*; Maekawa, Sadamichi; Saito, Eiji

Nature Physics, 12, p.52 - 56, 2016/01

 Times Cited Count:44 Percentile:5.98(Physics, Multidisciplinary)

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