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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

Laser control of magnonic topological phases in antiferromagnets

Nakata, Koki; Kim, S. K.*; Takayoshi, Shintaro*

Physical Review B, 100(1), p.014421_1 - 014421_9, 2019/07

 Times Cited Count:2 Percentile:61.08(Materials Science, Multidisciplinary)

We study the laser control of magnon topological phases induced by the Aharonov-Casher effect in insulating antiferromagnets (AFs). Using Floquet formalism, we study nonequilibrium magnon dynamics away from the adiabatic limit and its effect on topological phenomena. Our results provide a handle to control and design magnon topological properties in the insulating AF, and thus open a new door to "photonic magnonics".

Journal Articles

Spinmotive force

Ieda, Junichi; Maekawa, Sadamichi

Spin Current (2nd Edition), p.69 - 92, 2017/11

 Times Cited Count:0 Percentile:100

This chapter reviews spinmotive force (SMF), which is an emerging concept that is responsible for generating spin current and electric voltage in magnetic conductors. The SMF is induced in magnetic nanostructures via the exchange interaction between conduction spin and magnetization. Various types of the spin electric fields are found: adiabatic, nonadiabatic, and their spin-orbit coupled equivalents. In experiment, the adiabatic contributions with/without spin-orbit coupling have been observed whereas detecting nonadiabatic effects is challenging. The SMF offers electrical detection of magnetization dynamics, which would allow us to monitor the elusive dynamics of antiferromagnets.

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

Spin-transfer torques in antiferromagnetic textures; Efficiency and quantification method

Yamane, Yuta*; Ieda, Junichi; Sinova, J.*

Physical Review B, 94(5), p.054409_1 - 054409_8, 2016/08

AA2016-0164.pdf:0.5MB

 Times Cited Count:16 Percentile:26.53(Materials Science, Multidisciplinary)

We formulate a theory of spin-transfer torques in antiferromagnets, which covers the small to large limits of the exchange coupling energy relative to the kinetic energy of the inter-sublattice electron dynamics. Our theory suggests a natural definition of the efficiency of spin-transfer torques in antiferromagnets in terms of well-defined material parameters, revealing that the charge current couples predominantly to the antiferromagnetic order parameter and the sublattice-canting moment in, respectively, the limits of large and small exchange coupling. The effects can be quantified by analyzing the antiferromagnetic spin-wave dispersions in the presence of charge current: in the limit of large exchange coupling the spin-wave Doppler shift always occurs, whereas, in the opposite limit, the only spin-wave modes to react to the charge current are ones that carry a pronounced sublattice-canting moment. The findings offer a framework for understanding and designing spin-transfer torques in antiferromagnets belonging to different classes of sublattice structures such as, e.g., bipartite and layered antiferromagnets.

Journal Articles

Spin pumping blocked by single-layer graphene

Haku, Satoshi*; Tashiro, Takaharu*; Nakayama, Hiroyasu*; Ieda, Junichi; Entani, Shiro; Sakai, Seiji; Ando, Kazuya*

Applied Physics Express, 8(7), p.073009_1 - 073009_3, 2015/07

 Times Cited Count:3 Percentile:80.78(Physics, Applied)

We found that the spin pumping in a Ni$$_{81}$$Fe$$_{19}$$/Pt bilayer is strongly suppressed by inserting single-layer graphene (SLG) at the interface. The spin pumping in the Ni$$_{81}$$Fe$$_{19}$$/Pt bilayer enhances the magnetization damping of the ferromagnetic layer, which is quantified from microwave frequency dependence of ferromagnetic resonance linewidth. We show that the enhancement of the magnetization damping due to the spin pumping disappears in a Ni$$_{81}$$Fe$$_{19}$$/SLG/Pt trilayer. This result indicates that the spin pumping is blocked by the atomic monolayer, demonstrating the crucial role of the interfacial short-range spin-exchange coupling in the spin pumping in metallic systems.

Oral presentation

Mechanical generation of spin current

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

no journal, , 

Spin current, a flow of spins, is a key concept in the field of spintronics. It is generated by using angular momentum conversion between magnetization, photon, electric current and so on. On the other hand, mechanical angular momentum due to mechanical motion has not been utilized for spin-current generation so far. In this talk, we discuss theoretical and experimental results for spin-current generation from mechanical motion. The spin-current generation by mechanical motion stems from the spin-rotation coupling, which is the fundamental interaction between spin angular momentum and rotational motion.

Oral presentation

Ultra-low energy spin wave dispersion of Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$

Shamoto, Shinichi; Matsuura, Masato*; Akatsu, Mitsuhiro*; Ito, Takashi; Nemoto, Yuichi*; Shibata, Kaoru

no journal, , 

no abstracts in English

Oral presentation

Spintronic micro-power generation

Ieda, Junichi

no journal, , 

Spintronics aims to harness both charge and spin degrees of freedom of electrons in condensed matter systems and opens fascinating new perspectives for both basic research and device technology. Cooperation of the spin-orbit interaction with the exchange interaction between the conduction electron spins and localized moment gives rise to a variety of phenomena that generate, control, and detect spin currents. In this talk, we present our contributions to developing new ways of micro-power generation based on spin currents, i.e., the spinmotive force, spin Seebeck effect, and spin hydrodynamic generation.

Oral presentation

Neutron scattering study on Y$$_3$$Fe$$_5$$O$$_{12}$$ under ultrasound irradiation

Shamoto, Shinichi; Matsuura, Masato*; Akatsu, Mitsuhiro*; Yasui, Yukio*; Ito, Takashi; Ieda, Junichi; Endo, Hitoshi*; Oda, Tatsuro*; Chang, L.-J.*; Nemoto, Yuichi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Neutron scattering study on Y$$_3$$Fe$$_5$$O$$_{12}$$ under ultrasound irradiation

Shamoto, Shinichi; Matsuura, Masato*; Akatsu, Mitsuhiro*; Yasui, Yukio*; Ito, Takashi; Ieda, Junichi; Endo, Hitoshi*; Oda, Tatsuro*; Chang, L.-J.*; Nemoto, Yuichi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Magnonic spin current-noise in insulating bulk magnets

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

no journal, , 

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. We theoretically discover that compared with a Poissonian shot noise of magnons in an insulating ferromagnetic junction, the magnonic shot noise is suppressed in the diffusive insulating bulk magnet and noise-to-current ratio (Fano factor) at low temperatures exhibits a universal behavior, i.e., the same suppression 1/3 as the one for electron transport in diffusive conductors, despite the difference of quantum-statistical properties.

Oral presentation

Quantum spin-current noise of magnons

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

no journal, , 

Using the Keldysh formalism, we calculate a magnonic current-noise and compare it with the current-noise of electrically charged electrons. We thus discuss the universality of current-noise against the difference of quantum-statistical properties of bosons and fermions.

Oral presentation

Laser control of magnonic topological phases in antiferromagnets

Nakata, Koki; Kim, S. K.*; Takayoshi, Shintaro*

no journal, , 

We study the laser control of magnon topological phases induced by the Aharonov-Casher effect in insulating antiferromagnets (AFs). Our results provide a handle to control and design magnon topological properties in the insulating AF.

14 (Records 1-14 displayed on this page)
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