Faculty | Department of Electrical and Electronic Engineering Research Institute of Industrial Technology Course of Electricity， Electronics and Communications |
---|---|

Position | Professor |

HomepageURL | |

Birthday |

Last Updated :2020/07/09

- - 2001 , Tohoku University
- - 1998 , Tohoku University
- - 1996 , Ritsumeikan University, College of Science and Engineering

- 2007 - 2010 , Kanagawa Institute of Technology, Center for Basic Education and Integrated Learning
- 2002 - 2007 , RIKEN

- Natural sciences, Magnetism, superconductivity, and strongly correlated systems

- Theory of electromagnetic wave propagation in ferromagnetic Rashba conductor, SHIBATA Junya, Journal of Applied Physics 123, 063902 (2018);, Journal of Applied Physics 123, 063902 (2018);, 123, (6) 063902-1 - 063902-35, 02 , Refereed
- Theory of Anomalous Optical Properties of Bulk Rashba Conductor, Junya Shibata, Akihito Takeuchi, Hiroshi Kohno, Gen Tatara, J. Phys. Soc. Jpn, J. Phys. Soc. Jpn, 85, (2) 033701-1 - 033701, 02 , Refereed
- Spin torques due to diffusive spin current in magnetic texture, Kazuhiro Hosono, Junya Shibata, Hiroshi Kohno, Yukio Nozaki, PHYSICAL REVIEW B, PHYSICAL REVIEW B, 87, (9) 094404-1 - 094404-8, 03
- Calculation of Nonlocal Spin Transfer Torque, Kazuhiro Hosono, Junya Shibata, Hiroshi Kohno, Yukio Nozaki, IEEE TRANSACTIONS ON MAGNETICS, IEEE TRANSACTIONS ON MAGNETICS, 48, (11) 4367 - 4370, 11
- Spin and charge transport induced by gauge fields in a ferromagnet, Junya Shibata, Hiroshi Kohno, PHYSICAL REVIEW B, PHYSICAL REVIEW B, 84, (18) 184408-1 - 184408-12, 11
- A brief review of field- and current-driven domain-wall motion, Junya Shibata, Gen Tatara, Hiroshi Kohno, JOURNAL OF PHYSICS D-APPLIED PHYSICS, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 44, (38) 384004-1 - 384004-18, 09
- Spin Hall Current and Spin-transfer Torque in Ferromagnetic Metal, Junya Shibata, INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009), INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009), 200, (2) 062026-1 - 062029-4
- Inverse Spin Hall Effect Driven by Spin Motive Force, Junya Shibata, Hiroshi Kohno, PHYSICAL REVIEW LETTERS, PHYSICAL REVIEW LETTERS, 102, (8) 086603-1 - 086603-4, 02
- Microscopic approach to current-driven domain wall dynamics, Gen Tatara, Hiroshi Kohno, Junya Shibata, PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 468, (6) 213 - 301, 11
- Theory of domain wall dynamics under current, Gen Tatara, Hiroshi Kohno, Junya Shibata, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 77, (3) 031003-1 - 031103-14, 03
- Magnetic vortex dynamics, Roman Antos, YoshiChika Otani, Junya Shibata, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 77, (3) 031004-1 - 031004-8, 03
- Nucleation and dynamics of magnetic vortices under spin-polarized current, Yoshinobu Nakatani, Junya Shibata, Gen Tatara, Hiroshi Kohno, Andre Thiaville, Jacques Miltat, PHYSICAL REVIEW B, PHYSICAL REVIEW B, 77, (1) 014439-1 - 014439-7, 01
- Gauge field formulation of adiabatic spin torques, Hiroshi Kohno, Junya Shibata, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 76, (6) 063710-1 - 063710-4, 06
- Spin torque and force due to current for general spin textures, Gen Tatara, Hiroshi Kohno, Junya Shibata, Yann Lemaho, Kyung-Jin Lee, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 76, (5) 054707-1 - 054707-13, 05
- Vortex motion in chilarity-controlled pair of magnetic disks, T. Kimura, Y. Otani, H. Masaki, T. Ishida, R. Antos, J. Shibata, APPLIED PHYSICS LETTERS, APPLIED PHYSICS LETTERS, 90, (13) 132501-1 - 132501-3, 03
- Theory of current-driven domain wall dynamics, G. Tatara, H. Kohno, J. Shibata, JOURNAL OF PHYSICS D-APPLIED PHYSICS, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 40, (5) 1257 - 1260, 03
- Magnetic vortex dynamics induced by spin-transfer torque, J. Shibata, Y. Nakatani, G. Tatara, H. Kohno, Y. Otani, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 310, (2) 2041 - 2042, 03
- Microscopic calculation of spin torques in disordered ferromagnets, Hiroshi Kohno, Gen Tatara, Junya Shibata, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 75, (11) 113706-1 - 113706-4, 11
- Control of domain wall pinning by a switchable magnetic gate, Masahiro Hara, Junya Shibata, Takashi Kimura, Yoshichika Otani, APPLIED PHYSICS LETTERS, APPLIED PHYSICS LETTERS, 89, (19) 192504-1 - 192504-3, 11
- Threshold current of domain wall motion under extrinsic pinning, beta-term and non-adiabaticity, Gen Tatara, Toshihiko Takayama, Hiroshi Kohno, Junya Shibata, Yoshinobu Nakatani, Hidetoshi Fukuyama, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 75, (6) 064708-1 - 064708-7, 06
- Detection of magnetic state in a nanoscale ferromagnetic ring by using ballistic semiconductor two-dimensional electron gas, M Hara, J Shibata, T Kimura, Y Otani, APPLIED PHYSICS LETTERS, APPLIED PHYSICS LETTERS, 88, (8) 082501-1 - 082501-3, 02
- Current-induced magnetic vortex motion by spin-transfer torque, J Shibata, Y Nakatani, G Tatara, H Kohno, Y Otani, PHYSICAL REVIEW B, PHYSICAL REVIEW B, 73, (2) 020403-1(R) - 020403-4(R), 01
- Current-induced domain nucleation in ferromagnet, J Shibata, G Tatara, H Kohno, Y Otani, IEEE TRANSACTIONS ON MAGNETICS, IEEE TRANSACTIONS ON MAGNETICS, 41, (10) 2595 - 2597, 10
- Effect of spin current on uniform ferromagnetism: Domain nucleation, J Shibata, G Tatara, H Kohno, PHYSICAL REVIEW LETTERS, PHYSICAL REVIEW LETTERS, 94, (7) 076601-1 - 076601-4, 02
- Magnetic vortex dynamics in a two-dimensional square lattice of ferromagnetic nanodisks, J Shibata, Y Otani, PHYSICAL REVIEW B, PHYSICAL REVIEW B, 70, (1) 012404-1 - 012404-4, 07
- Dynamics of nano-scale magnetic vortices in ferromagnetic dot arrays, J Shibata, K Shigeto, Y Otani, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 272, (3) 1688 - 1689, 05
- Method of collective degrees of freedom in spin-coherent-state path integral, J Shibata, S Takagi, PHYSICS OF ATOMIC NUCLEI, PHYSICS OF ATOMIC NUCLEI, 64, (12) 2206 - 2211, 12

- Inverse Spin Hall Effect Driven by Spin Motive Force, Junya Shibata, Hiroshi Kohno, PHYSICAL REVIEW LETTERS, 102, 2009 02 , The spin Hall effect is a phenomenon in which an electric field induces a spin Hall current. In this Letter, we examine the inverse effect that, in a ferromagnetic conductor, a charge Hall current is induced by a spin motive force, or a spin-dependent effective "electric" field E(s), arising from the time variation of magnetization texture. By considering skew-scattering and side-jump processes due to spin-orbit interaction at impurities, we obtain the Hall current density as sigma(SH)nxE(s), where n is the local spin direction and sigma(SH) is the spin Hall conductivity. The Hall angle due to the spin motive force is enhanced by a factor of P(-2) compared to the conventional anomalous Hall effect due to the ordinary electric field, where P is the spin polarization of the current. The Hall voltage is estimated for a field-driven domain-wall oscillation in a ferromagnetic nanowire.
- Microscopic approach to current-driven domain wall dynamics, Gen Tatara, Hiroshi Kohno, Junya Shibata, PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 468, (6) 213 - 301, 2008 11 , This review describes in detail the essential techniques used in microscopic theories on spintronics. We have investigated the domain wall dynamics induced by ail electric current, based on the s-d exchange model. The domain wall is treated as rigid anti planar and is described by two collective coordinates: the position and angle of wall magnetization. file effect of conduction electrons on the domain wall dynamics is calculated in the case of slowly varying spin structure (close to the adiabatic limit) by use of a gauge transformation. The spin-transfer torque and force oil the wall are expressed by Feynman diagrams and calculated systematically using non-equilibrium Green's functions, treating electrons fully quantum mechanically. The wall dynamics is discussed, based on two coupled equations of motion derived for two collective coordinates. The force is related to electron transport properties, resistivity, and the Hall effect. The effect of conduction electron spin relaxation on the torque and wall dynamics is also studied. (C) 2008 Elsevier B.V. All rights reserved.
- Theory of domain wall dynamics under current, Gen Tatara, Hiroshi Kohno, Junya Shibata, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 77, 2008 03 , Microscopic theory of domain wall dynamics under electric current is reviewed. Domain wall is treated as rigid and planar. The spin-transfer torque and forces on the wall are derived based on the s-d exchange interaction between localized spins and conduction electrons, treating non-adiabaticity expressed by the gauge field perturbatively. Effect of spin relaxation is also studied.
- Magnetic vortex dynamics, Roman Antos, YoshiChika Otani, Junya Shibata, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 77, 2008 03 , We review the recent theoretical and experimental achievements on dynamics of spin vortices in patterned ferromagnetic elements. We first demonstrate the theoretical background of the research topic and briefly list the analytical and experimental approaches dealing with magnetic vortices. Then we report on the most remarkable studies devoted to steady state vortex excitations, switching processes, and coupled-vortex dynamic phenomena including the design of artificial crystals where the micromagnetic energy transfer takes place via the magnetic dipolar interaction among excited vortices. Finally we summarize the present state of the research with respect to novel prospects from both the fundamental and the application viewpoints.
- Nucleation and dynamics of magnetic vortices under spin-polarized current, Yoshinobu Nakatani, Junya Shibata, Gen Tatara, Hiroshi Kohno, Andre Thiaville, Jacques Miltat, PHYSICAL REVIEW B, 77, 2008 01 , Spin-polarized current in a ferromagnet is known to lead to the instability of the uniformly magnetized state. In this paper, it is demonstrated by micromagnetic simulations that, in films or wide wires, the above instability is followed by the formation of magnetic vortices. Subsequent magnetization dynamics is also studied in terms of vortices, which includes pair dynamics and pair annihilation. Using a simple analytical model that considers the vortices as points, the dynamics of two interacting vortices under the current is classified according to their vorticity and polarity. This explains well the essential features of the simulation results.
- Gauge field formulation of adiabatic spin torques, Hiroshi Kohno, Junya Shibata, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 76, 2007 06 , Previous calculation of spin torques for small-amplitude magnetization dynamics around a uniformly magnetized state [J. Phys. Soc. Jpn. 75 (2006) 113706] is extended here to the case of finite-amplitude dynamics. This is achieved by introducing an "adiabatic" spin frame for conduction electrons, and the associated SU(2) gauge field. In particular, the Gilbert damping is shown to arise from the time variation of the spin-relaxation source terms in this new frame, giving a new physical picture of the damping. The present method will allow a "first-principle" derivation of spin torques without any assumptions such as rotational symmetry in spin space.
- Spin torque and force due to current for general spin textures, Gen Tatara, Hiroshi Kohno, Junya Shibata, Yann Lemaho, Kyung-Jin Lee, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 76, 2007 05 , The nonadiabatic correction to spin transfer torque arising from fast-varying spin texture is calculated treating the conductions electron fully quantum mechanically. The torque is nonlocal in space, and is shown to be equivalent to a force (due to momentum transfer) acting on the center of mass of the texture. Another kind of force exists in the adiabatic regime, and it is identified to be of topological origin. These forces are shown to be the counter-reactions of electric transport properties, resistivity and the Hall effect.
- Vortex motion in chilarity-controlled pair of magnetic disks, T. Kimura, Y. Otani, H. Masaki, T. Ishida, R. Antos, J. Shibata, APPLIED PHYSICS LETTERS, 90, (13) 1325011 - 3, 2007 03 , The authors investigate the influence of the vortex chirality on the magnetization processes of a magnetostatically coupled pair of magnetic disks. The magnetic vortices with opposite chiralities are realized by introducing asymmetry into the disks. The motion of the paired vortices are studied by measuring the magnetoresistance with a lock-in resistance bridge technique. The vortex annihilation process is found to depend on the moving directions of the magnetic vortices. The experimental results are well reproduced by the micromagnetic simulation. (c) 2007 American Institute of Physics.
- Microscopic calculation of spin torques and forces, H. Kohno, G. Tatara, J. Shibata, Y. Suzuki, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 310, (2) 2020 - 2022, 2007 03 , Spin torques, that is, effects of conduction electrons on magnetization dynamics, are calculated microscopically in the first order in spatial gradient and time derivative of magnetization. Special attention is paid to the so-called beta-term and the Gilbert damping, alpha, in the presence of electrons' spin-relaxation processes, which are modeled by quenched magnetic impurities. Two types of forces that the electric/spin current exerts on magnetization are identified based on a general formula relating the force to the torque. (c) 2006 Elsevier B.V. All rights reserved.
- Magnetic vortex dynamics induced by spin-transfer torque, J. Shibata, Y. Nakatani, G. Tatara, H. Kohno, Y. Otani, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 310, (2) 2041 - 2042, 2007 03 , We theoretically study the dynamics of a magnetic vortex under spin-polarized electric current in ferromagnets. The equation of motion of the vortex in terms of collective coordinates is derived. We compare our theory with recent experiments for current-induced vortex displacement and resonance motion in a ferromagnetic nanodot. Our estimate for the displacement and the resonance frequency shows a good agreement with the experiment. We also study the current-induced motion of a vortex wall in a ferromagnetic thin wire. (c) 2006 Elsevier B.V. All rights reserved.
- Theory of current-driven domain wall dynamics, G. Tatara, H. Kohno, J. Shibata, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 40, (5) 1257 - 1260, 2007 03 , The motion of a planar domain wall in a nanoscale ferromagnetic wire under electric current is studied, based on a microscopic description. In the adiabatic case, the domain wall is driven by spin torque ( spin transfer), and there is an intrinsic pinning arising from hard-axis anisotropy energy. Effects of extrinsic pinning and spin relaxation ( beta-term) on the threshold current are discussed.
- Control of domain wall pinning by a switchable magnetic gate, Masahiro Hara, Junya Shibata, Takashi Kimura, Yoshichika Otani, APPLIED PHYSICS LETTERS, 89, 2006 11 , Magnetically coupled domain wall pinning has been investigated by means of an attached pair of ferromagnetic wires. The magnetic configuration of the paired wires (parallel or antiparallel) can be controlled by applying an external magnetic field along the wires. The strength of the pinning due to the magnetic interaction between the domain wall and the paired wires shows a significant difference between the parallel and antiparallel configurations, which is well reproduced by a micromagnetics simulation.
- Microscopic calculation of spin torques in disordered ferromagnets, Hiroshi Kohno, Gen Tatara, Junya Shibata, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 75, 2006 11 , Effects of conduction electrons on magnetization dynamics, represented by spin torques, are calculated microscopically in the first order in spatial gradient and time derivative of magnetization. Special attention is paid to the so-called beta-term and the Gilbert damping, alpha, in the presence of electrons' spin-relaxation processes, which are modeled by quenched magnetic (and spin-orbit) impurities. It is shown that these two torque terms actually arise from the spin relaxation processes, both transverse and longitudinal, and their coefficients are different, alpha not equal beta, in general. These features hold for both localized and itinerant models for ferromagnetism.
- Threshold current of domain wall motion under extrinsic pinning, beta-term and non-adiabaticity, Gen Tatara, Toshihiko Takayama, Hiroshi Kohno, Junya Shibata, Yoshinobu Nakatani, Hidetoshi Fukuyama, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 75, 2006 06 , Threshold current of domain wall motion under spin-polarized electric current in ferromagnets is theoretically studied based on the equation of motion of a wall in terms of collective coordinates. Effects of non-adiabaticity and a so-called beta-term in Landau-Lifshitz equation, which are described by the same term in the equation of motion of a wall, are taken into account as well as extrinsic pinning. It is demonstrated that there are four different regimes characterized by different dependence of threshold on extrinsic pinning, hard-axis magnetic anisotropy, non-adiabaticity and beta.
- Detection of magnetic state in a nanoscale ferromagnetic ring by using ballistic semiconductor two-dimensional electron gas, M Hara, J Shibata, T Kimura, Y Otani, APPLIED PHYSICS LETTERS, 88, 2006 02 , We have developed a method of measuring magnetization process in a ferromagnetic ring by analyzing a characteristic response of a semiconductor two-dimensional electron gas (2DEG) lying beneath the ring. A 2DEG microcross structure is formed underneath a ferromagnetic ring to detect the position of paired domain walls of the onion state. The variation of the bend resistance due to the rotation of the paired domain walls is quantitatively reproduced by a semiclassical billiard model. (c) 2006 American Institute of Physics.
- Current-induced magnetic vortex motion by spin-transfer torque, J Shibata, Y Nakatani, G Tatara, H Kohno, Y Otani, PHYSICAL REVIEW B, 73, 2006 01 , We investigate the dynamics of a magnetic vortex driven by spin-transfer torque due to spin current in the adiabatic case. The vortex core represented by collective coordinate experiences a transverse force proportional to the product of spin current and gyrovector, which can be interpreted as the geometric force determined by topological charges. We show that this force is just a reaction force of Lorentz-type force from the spin current of conduction electrons. Based on our analyses, we propose analytically and numerically a possible experiment to check the vortex displacement by spin current in the case of single magnetic nanodot.
- Current-induced domain nucleation in ferromagnet, J Shibata, G Tatara, H Kohno, Y Otani, IEEE TRANSACTIONS ON MAGNETICS, 41, (10) 2595 - 2597, 2005 10 , A key mechanism of the current-induced magnetization dynamics is the spin torque from a spin polarized current (spin current), which couples to spatial gradient of magnetization. Recently, it was pointed out that a large spin current applied to a uniform ferromagnet leads to a spin-wave instability. In this paper, we show that such instability is absent in a state containing a domain wall. This may indicate that nucleation of magnetic domains occurs above a certain critical spin current. This scenario is supported by an explicit energy comparison between the uniformly magnetized state and the domain-wall state under spin current.
- Effect of spin current on uniform ferromagnetism: Domain nucleation, J Shibata, G Tatara, H Kohno, PHYSICAL REVIEW LETTERS, 94, 2005 02 , A large spin current applied to a uniform ferromagnet leads to a spin-wave instability as pointed out recently. In this Letter, it is shown that such spin-wave instability is absent in a state containing a domain wall, which indicates that nucleation of magnetic domains occurs above a certain critical spin current. This scenario is supported also by an explicit energy comparison of the two states under spin current.
- Magnetic vortex dynamics in a two-dimensional square lattice of ferromagnetic nanodisks, J Shibata, Y Otani, PHYSICAL REVIEW B, 70, 2004 07 , The dynamics of magnetostatically coupled vortices in ferromagnetic two-dimensional (2D) nanodisk arrays is theoretically investigated using the rigid vortex model and Thiele's equation whereby the circular motion with the lowest energy for each vortex core is described. We present here dispersion relations and density of states for eigenfrequencies of coherently rotating vortices with ordered core polarizations. This behavior is analogous to the lattice vibration of a 2D molecule bound with a dipolar interaction.
- Dynamics of nano-scale magnetic vortices in ferromagnetic dot arrays, J Shibata, K Shigeto, Y Otani, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 272, (3) 1688 - 1689, 2004 05 , We investigate analytically and numerically the dynamics of magnetostatically coupled vortices in ferromagnetic dot arrays. Eigenfrequencies of rotational motion of vortex core in two nano-dots are calculated by using the rigid vortex model and Thiele's equation where collective degrees of freedom describe the motion of each vortex core. We further extend the model to array of magnetostatically coupled N x N dots in two-dimensional tetragonal lattice, which is found to exhibit characteristic dispersion relation for eigenfrequencies. (C) 2003 Published by Elsevier B.V.
- Method of collective degrees of freedom in spin-coherent-state path integral, J Shibata, S Takagi, PHYSICS OF ATOMIC NUCLEI, 64, (12) 2206 - 2211, 2001 12 , We present a detailed field-theoretical description of those collective degrees of freedom (CDF) which are relevant to study macroscopic quantum dynamics of a quasi-one-dimensional ferromagnetic domain wall. We apply the spin-coherent-state path integral in the proper discrete time formalism (a) to extract the relevant CDFs, namely, the center position and the chirality of the domain wall, which originate from the translation and the rotation invariances of the system in question, and (b) to derive an effective action for the CDFs by elimination of environmental zero modes with the help of the Faddeev-Popov technique. The resulting effective action turns out to be such that both the center position and the chirality can be formally described by a boson-coherent-state path integral. However, this is only formal; there is a subtle departure from the latter. (C) 2001 MAIK "Nauka/Interperiodica".

- 特願2006-251737
- 特願2005-006861