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Journal Articles

Intrinsic surface magnetic anisotropy in Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$ as the origin of low-magnetic-field behavior of the spin Seebeck effect

Uchida, Kenichi*; Oe, Junichiro*; Kikkawa, Takashi*; Daimon, Shunsuke*; Hou, D.*; Qiu, Z.*; Saito, Eiji

Physical Review B, 92(1), p.014415_1 - 014415_8, 2015/07

 Times Cited Count:26 Percentile:77.37(Materials Science, Multidisciplinary)

Journal Articles

Generation of spin currents in the skyrmion phase of a helimagnetic insulator Cu$$_2$$OSeO$$_3$$

Hirobe, Daichi*; Shiomi, Yuki*; Shimada, Yuki*; Oe, Junichiro*; Saito, Eiji

Journal of Applied Physics, 117(5), p.053904_1 - 053904_6, 2015/02

 Times Cited Count:8 Percentile:37.13(Physics, Applied)

Journal Articles

Unidirectional spin-wave heat conveyer

An, Toshu*; Vasyuchka, V. I.*; Uchida, Kenichi*; Chumak, A. V.*; Yamaguchi, Kazuya*; Harii, Kazuya; Oe, Junichiro*; Jungfleisch, M. B.*; Kajiwara, Yosuke*; Adachi, Hiroto; et al.

Nature Materials, 12(6), p.549 - 553, 2013/06

 Times Cited Count:102 Percentile:96.17(Chemistry, Physical)

Journal Articles

Spin-motive force due to a gyrating magnetic vortex

Tanabe, Kenji*; Chiba, Daichi*; Oe, Junichiro*; Kasai, Shinya*; Kono, Hideo*; Barnes, S. E.*; Maekawa, Sadamichi; Kobayashi, Kensuke*; Ono, Teruo*

Nature Communications (Internet), 3, p.845_1 - 845_5, 2012/05

 Times Cited Count:37 Percentile:83.43(Multidisciplinary Sciences)

Journal Articles

Time-domain observation of the spinmotive force in permalloy nanowires

Hayashi, Masamitsu*; Ieda, Junichi; Yamane, Yuta; Oe, Junichiro*; Takahashi, Yukiko*; Mitani, Seiji*; Maekawa, Sadamichi

Physical Review Letters, 108(14), p.147202_1 - 147202_5, 2012/04

 Times Cited Count:30 Percentile:81.09(Physics, Multidisciplinary)

Spinmotive force associated with a moving domain wall is observed directly in permalloy nanowires using real time voltage measurements with proper subtraction of the electromotive force. Whereas the wall velocity exhibits nonlinear dependence on a magnetic field, the generated voltage increases linearly with the field. We show that the sign of the voltage reverses when the wall propagation direction is altered. Numerical simulations explain quantitatively these features of spinmotive force and indicate that the spinmotive force scales with the field even in a field range where the wall motion is no longer associated with periodic structure transformation.

Journal Articles

Continuous generation of spinmotive force in a patterned ferromagnetic film

Yamane, Yuta; Sasage, Kohei*; An, Toshu*; Harii, Kazuya*; Oe, Junichiro*; Ieda, Junichi; Barnes, S. E.*; Saito, Eiji; Maekawa, Sadamichi

Physical Review Letters, 107(23), p.236602_1 - 236602_4, 2011/11

 Times Cited Count:39 Percentile:85.21(Physics, Multidisciplinary)

Journal Articles

Spinmotive force due to intrinsic energy of ferromagnetic nanowires

Yamane, Yuta; Ieda, Junichi; Oe, Junichiro*; Barnes, S. E.*; Maekawa, Sadamichi

Applied Physics Express, 4(9), p.093003_1 - 093003_3, 2011/09

 Times Cited Count:8 Percentile:37.66(Physics, Applied)

Journal Articles

Equation-of-motion approach of spin-motive force

Yamane, Yuta; Ieda, Junichi; Oe, Junichiro*; Barnes, S. E.*; Maekawa, Sadamichi

Journal of Applied Physics, 109(7), p.07C735_1 - 07C735_3, 2011/04

 Times Cited Count:16 Percentile:59.6(Physics, Applied)

Journal Articles

Numerical study on the spin Seebeck effect

Oe, Junichiro; Adachi, Hiroto; Takahashi, Saburo; Maekawa, Sadamichi

Physical Review B, 83(11), p.115118_1 - 115118_5, 2011/03

 Times Cited Count:43 Percentile:85.67(Materials Science, Multidisciplinary)

Thermally driven spin-wave spin currents in ferromagnetic (FM) materials and a resulting measurable electric signal in a normal metal (NM) probe placed on FM are theoretically investigated. We develop the numerical technique for calculating a spin Seebeck signal detected by the NM probe that converts the spin current to the charge current. By taking into account the fluctuation-dissipation theorem for thermally fluctuating spins at the interface of a FM/NM junction, the spin current is induced in the NM probe via an exchange interaction when the FM feels the temperature gradient. Numerical simulation clarifies the role of the sample boundary on the spatial distribution of the spin current both in FM and NM. The spin-wave spin current that flows parallel to the heat current is also investigated.

Journal Articles

Linear-response theory of spin Seebeck effect in ferromagnetic insulators

Adachi, Hiroto; Oe, Junichiro; Takahashi, Saburo; Maekawa, Sadamichi

Physical Review B, 83(9), p.094410_1 - 094410_6, 2011/03

 Times Cited Count:204 Percentile:98.59(Materials Science, Multidisciplinary)

We formulate a linear response theory of the spin Seebeck effect, i.e., a spin voltage generation from heat current flowing in a ferromagnet. Our approach focuses on the collective magnetic excitation of spins, i.e., magnons. We show that the linear-response formulation provides us with a qualitative as well as quantitative understanding of the spin Seebeck effect observed in a prototypical magnet, yttrium iron garnet.

Journal Articles

Gigantic enhancement of spin Seebeck effect by phonon drag

Adachi, Hiroto; Uchida, Kenichi*; Saito, Eiji; Oe, Junichiro; Takahashi, Saburo; Maekawa, Sadamichi

Applied Physics Letters, 97(25), p.252506_1 - 252506_3, 2010/12

 Times Cited Count:128 Percentile:96.63(Physics, Applied)

We investigate both theoretically and experimentally a gigantic enhancement of the spin Seebeck effect in a prototypical magnet LaY$$_{2}$$Fe$$_{5}$$O$$_{12}$$ at low temperatures. Our theoretical analysis sheds light on the important role of phonons: the spin Seebeck effect is enormously enhanced by nonequilibrium phonons that drag low-lying spin excitations. We further argue that this scenario gives a clue to understand the observation of the spin Seebeck effect that is unaccompanied by a global spin current, and predict that the substrate condition affects the observed signal.

Journal Articles

Spin Seebeck insulator

Uchida, Kenichi*; Xiao, J.*; Adachi, Hiroto; Oe, Junichiro; Takahashi, Saburo; Ieda, Junichi; Ota, Takeru*; Kajiwara, Yosuke*; Umezawa, Hiromitsu*; Kawai, Hirotaka*; et al.

Nature Materials, 9(11), p.894 - 897, 2010/11

 Times Cited Count:884 Percentile:99.87(Chemistry, Physical)

Thermoelectric generation is an essential function in future energy-saving technologies. However, it has so far been an exclusive feature of electric conductors, a situation which limits its application; conduction electrons are often problematic in the thermal design of devices. Here we report electric voltage generation from heat flowing in an insulator. We reveal that, despite the absence of conduction electrons, the magnetic insulator LaY$$_{2}$$Fe$$_{5}$$O$$_{12}$$ can convert a heat flow into a spin voltage. Attached Pt films can then transform this spin voltage into an electric voltage as a result of the inverse spin Hall effect. The experimental result require us to introduce a thermally activated interface spin exchange between LaY$$_{2}$$Fe$$_{5}$$O$$_{12}$$ and Pt. Our findings extend the range of potential materials for thermoelectric applications and provide a crucial piece of information for understanding the physics of the spin Seebeck effect.

Journal Articles

New numerical approach for studying diluted magnetic semiconductors

Oe, Junichiro; Gu, B.; Maekawa, Sadamichi

Kotai Butsuri, 45(5), p.269 - 278, 2010/06

We report a new combined numerical approach for studying diluted magnetic semiconductors (DMS). In this approach, realistic parameters obtained by the ${it ab initio}$ calculation are used for performing quantum Monte Carlo calculations. We show that the proposed approach well describes the magnetic properties of DMS and can be used for designing the new DMS materials which has high Curie temperatures.

Journal Articles

Relationship between tensile curve and indentation load-depth curve for a Ni-base alloy with microstructures by cold work and aging

Yamamoto, Junichiro*; Futakawa, Masatoshi; Kurata, Yuji; Naoe, Takashi*

Nihon Kikai Gakkai Kanto Shibu Ibaraki Koenkai (2002) Koen Rombunshu, p.1 - 2, 2002/09

no abstracts in English

Oral presentation

Spin-wave-mediated spin Seebeck effect

Adachi, Hiroto; Oe, Junichiro; Takahashi, Saburo; Maekawa, Sadamichi

no journal, , 

It has been a conventional wisdom that a spin current is carried by conduction electrons in metals. However, it was recently demonstrated that there exist another type of spin current carried by low-lying excitations of localized spins, i.e., the spin-wave excitations. One of the important feature of the latter spin current, which we call here a spin-wave spin current, is that it can propagate over a distance as long as several millimeters. Moreover, a recent report on the spin Seebeck effect in an insulating magnet provide us with a good opportunity to discuss the scenario of spin-wave-mediated spin Seebeck effect. In this talk, we focus on the spin Seebeck effect observed in an insulating magnet of yttrium iron garnet, and discuss the scenario of spin-wave-mediated spin Seebeck effect.

Oral presentation

Numerical study on the spin Seebeck effect in ferromagnetic insulators

Oe, Junichiro; Adachi, Hiroto; Takahashi, Saburo; Maekawa, Sadamichi

no journal, , 

In this report, we show the numerical study on the spin Seebeck effect by considering the magnetization dynamics in the presence of thermal gradient. The dynamics of the magnetization is given by solving the Landau-Lifshitz-Gilbert equation. We introduce the random magnetic field originated from finite temperatures which depends on the position. We calculate the spin current driven by the magnon in ferromagnetic sample. We also discuss the spin pumping to the normal probe attached to the sample for detecting the spin current.

Oral presentation

Numerical study on the thermal spin transport in ferromagnetic insulators

Adachi, Hiroto; Takahashi, Saburo; Maekawa, Sadamichi; Oe, Junichiro

no journal, , 

We report the theoretical study on the thermal spin transport in ferromagnetic insulators. By using the fluctuation-dissipation theorem, we derive a random torque acting on the magnetic moment at the finite temperature. The numerical results shows the propagating spin wave that is driven by the thermal gradient. Furthermore, we argue a measurable voltage induced by the inverse spin Hall effect by using realistic parameters of actual setup.

Oral presentation

Domain wall motion due to wire-shape effect, and spin-motive force

Yamane, Yuta; Ieda, Junichi; Oe, Junichiro; Maekawa, Sadamichi

no journal, , 

no abstracts in English

Oral presentation

Numerical study on the thermally driven spin-wave spin current

Oe, Junichiro; Adachi, Hiroto; Takahashi, Saburo; Maekawa, Sadamichi

no journal, , 

Recently, the relation between the heat current and the spin current has much attracted from the view of the spintronics applications. The heat current induces the spin current, the spin Seebeck effect, has been discovered not only inferromagnetic metals but also in ferromagnetic semiconductors and ferromagnetic insulators. In this reports, we investigate the spin Seebeck effect by using the numerical simulation. We focus on the dynamics of the magnetization in the presence of the fluctuating torque which represents finite temperatures. The spin current is driven by the magnetization dynamics and converted to the charge current in a normal metal probe. We use the Landau-Lifshitz-Gilbert equation for calculating the magnetization dynamics and the diffusion equation for the dynamics of the conduction electrons. Our results show good agreement with the experimental results qualitatively.

Oral presentation

Theoretical analysis of thermal spin current mediated by collective excitations, 3

Adachi, Hiroto; Oe, Junichiro; Takahashi, Saburo; Maekawa, Sadamichi

no journal, , 

no abstracts in English

35 (Records 1-20 displayed on this page)