Y. Nakatani

University of Electro-Communications

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N. Hayashi

University of California, Santa Cruz

Y. Uesaka

Kanazawa University

Teruo Ono

Kyoto University Institute for Chemical Research

Hiroshi Fukushima

National Cancer Institute

K. Yamada

Gifu University

Daichi Chiba

Osaka University

Shunsuke Fukami

Spintronics Research Network of Japan

S. Kasai

University of Yamanashi

Tomohiro Koyama

Osaka University

N. Ishiwata

NEC (Japan)

Cooperative Institutions

Tohoku University

The University of Tokyo

Spintronics Research Network of Japan

Kyoto University

Osaka University

Japan Science and Technology Agency

Hitachi (Japan)

University of Electro-Communications

Kyoto University Institute for Chemical Research

National Institute of Advanced Industrial Science and Technology

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Computer imulation of thermal fluctuation of a fine magnetic particle

IEEE International Magnetics Conference (1999)

Y. Nakatani N. Hayashi Y. Uesaka Hiroshi Fukushima

The influence of thermal fluctuation on magnetic recording media is considered to be an important factor which limits recording density and has been investigated by computer simulation [1]-[3].

Particle (ecology)

10.1109/intmag.1999.838021

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Citations (0)

Read/write properties of oriented longitudinal recording media

Journal of Magnetism and Magnetic Materials (2001)

Y. Uesaka Y. Nakatani N. Hayashi Hiroshi Fukushima

Recording media

Area density

Thermal Stability

10.1016/s0304-8853(01)00405-x

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Citations (2)

Nucleation and dynamics of magnetic vortices under spin-polarized current

Physical Review B (2008)

Y. Nakatani Junya Shibata Gen Tatara Hiroshi Kohno A. Thiaville

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.

Polarity (international relations)

Vortex state

Dynamics

Magnetization dynamics

10.1103/physrevb.77.014439

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Citations (26)

Effect of grain size on cluster size

Journal of Applied Physics (2005)

Hiraku Endo Y. Uesaka Y. Nakatani N. Hayashi Hiroshi Fukushima

A cluster size of a perpendicular medium was calculated from the correlation between grains in M-H loops. The cluster size was affected by physical properties as follows. When grain size is small and exchange stiffness constant A is not zero, the cluster size increases with decreasing grain-size. The increment of the cluster size decreases with increasing grain size distribution. The cluster size divided by the average grain size (normalized cluster size) increases with an increasing intergranular exchange coupling constant he. The normalized cluster size can be estimated from the grain-size distribution and the intergranular exchange coupling constant.

Cluster size

10.1063/1.1852331

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Citations (3)

Observation of magnetic domain wall motion induced by adiabatic spin transfer torque in Co/Ni nano-wires

Extended Abstracts of the 2020 International Conference on Solid State Devices and Materials (2011)

Tsukasa Koyama Kohei Ueda Daichi Chiba Shunsuke Fukami H. Tanigawa

Spin-transfer torque

Domain wall (magnetism)

10.7567/ssdm.2011.n-9-2

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Proposal for quantifying the Dzyaloshinsky–Moriya interaction by domain walls annihilation measurement

Japanese Journal of Applied Physics (2014)

Ryo Hiramatsu Kab‐Jin Kim Y. Nakatani Takahiro Moriyama Teruo Ono

We show that the magnitude of the Dzyaloshinsky–Moriya interaction (DMI) can be determined by a field-driven domain-walls (DWs) annihilation measurement. It is predicted that the DMI induces antiparallel Néel DWs which form a metastable 360° DW when they approach to each other. We find that an annihilation field, over which two DWs collide and vanish, is proportional to the magnitude of the DMI. This result suggests that the DMI can be quantified by a simple measurement of the annihilation field.

Annihilation

Antiparallel (mathematics)

Metastability

10.7567/jjap.53.108001

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Citations (14)

Analysis of MAMMOS Readout from Crescent Domains Using a Blue Laser

Transactions of the Magnetics Society of Japan (2002)

Susumu Imai Y. Nakatani Hiroyuki Awano O. Ishizaki Norio Ota

In the ongoing effort to achieve ultra high density Magneto-Optical recording, Laser Pumped Magnetic Field Modulation (LP-MFM) and Magnetic Amplifying Magneto-Optical System (MAMMOS) are considered promising methods. Using LP-MFM, crescent domains are recorded in a recording layer. Micro-magnetic simulations for the MAMMOS readout have already been reported assuming a crescent domain and red laser irradiation. Huth's equation simulations for the MAMMOS readout have also been reported assuming a circular recorded domain and blue laser irradiation. Micro-magnetic simulations for the MAMMOS readout assuming a blue laser irradiation, however, have not so far been reported. This paper presents the analysis of the combination of a 405nm blue laser and the MAMMOS readout from crescent recorded domains using the micro-magnetic simulations. In this work, MAMMOS readout from a crescent recorded domain is shown to be possible even with blue laser irradiation.

Blue laser

10.3379/tmjpn2001.2.297

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Citations (0)

24aPS-29 Additivity of magnetic domain wall velocities induced by current and field

Meeting abstracts of the Physical Society of Japan (2012)

Takeshi Koyama K. Ueda Daichi Chiba Shunsuke Fukami N. Ishiwata

Additive function

Source

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Switching of Single Hexagonal Particles with Nonuniform Magnetic Properties

Japanese Journal of Applied Physics (1995)

Y. Uesaka Y. Nakatani N. Hayashi

Switching fields of hexagonal particles with nonuniform magnetic properties are investigated using computer simulation. The switching field of a hexagonal particle with a low anisotropy energy constant ( K u ) region at a corner of all three thickness layers is lower than that of the uniform particle when the field is applied almost perpen-dicular to the hexagonal plane. However, when the field is applied almost parallel to the hexagonal plane, the switching field of the nonuniform hexagonal particle is similar to that of the uniform particle. A hexagonal particle with a low K u region at the center also switches in a lower field than the uniform particle does when the field is applied perpendicular to the hexagonal plane. The switching field of a hexagonal particle with low K u region in the surface layer is almost the same as that of a uniform particle.

Particle (ecology)

10.1143/jjap.34.6056

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Citations (6)

Electrical rectification effect in single domain magnetic microstrips: A micromagnetics-based analysis

Journal of Applied Physics (2008)

A. Thiaville Y. Nakatani

Upon passing an ac electrical current along magnetic micro- or nanostrips, the measurement of a dc voltage that depends sensitively on current frequency and applied field has been recently reported by Yamaguchi et al. [Appl. Phys. Lett. 90, 182507 (2007); e-print arXiv:0710.2172; Phys. Rev. B 78, 104401 (2008)]. It was attributed to the excitation of spin waves by the spin transfer torque, leading to a time-varying anisotropic magnetoresistance, and by mixing of ac current and resistance to a dc. voltage. We have performed a quantitative analysis by micromagnetics including the spin transfer torque terms considered usually of this situation. The signals found from the spin transfer torque effect are several orders of magnitude below the experimental values, even if a static inhomogeneity of magnetization (the so-called ripple) is taken into account. On the other hand, the presence of a small nonzero average Oersted field is shown to be consistent with the full set of experimental results, both qualitatively and quantitatively. We examine, quantitatively, several sources for this average field and point to the contacts of the sample as a likely origin.

Micromagnetics

Spin-transfer torque

10.1063/1.3006005

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Citations (14)