Yamanoi, Kazuto



Faculty of Science and Technology, Department of Physics (Yagami)


Research Associate/Assistant Professor/Instructor

Other Affiliation 【 Display / hide

  • 理学部・物理学科, 助教


Papers 【 Display / hide

  • Magnetic dynamics of quasi-Antiferromagnetic layer fabricated by 90° magnetic coupling

    Horiike S., Nagashima G., Kurokawa Y., Zhong Y., Yamanoi K., Tanaka T., Matsuyama K., Yuasa H.

    Japanese Journal of Applied Physics (Japanese Journal of Applied Physics)  59 ( SG )  2020.04

    ISSN  00214922

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    © 2020 The Japan Society of Applied Physics. In this study, we fabricated quasi-Antiferromagnetic (AFM) layers and investigated the magnetic dynamics of quasi-AFM in both an experiment and simulation. Quasi-AFM has multi domains with alternating antiparallel magnetization, which can be realized by using 90° magnetic coupling between two ferromagnetic layers. In magnetic resonance measurement, a frequency and damping constant of CoFe-based quasi-AFM are higher than those of conventional CoFe. Likewise, in micromagnetic simulation, we obtained the spin torque oscillation in Quasi-AFM with high frequency. This suggests the possibility of a novel material with the high frequency wave generator without a stray field, like antiferromagnetic materials.

  • Thermal Spin-Valve Effect in Magnetic Multi-layered Nanowires

    Asam N., Yamanoi K., Ohnishi K., Kimura T.

    Journal of Superconductivity and Novel Magnetism (Journal of Superconductivity and Novel Magnetism)  32 ( 10 ) 3109 - 3113 2019.10

    ISSN  15571939

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    © 2019, Springer Science+Business Media, LLC, part of Springer Nature. We have investigated the influence of the spin-dependent scattering on the heat transports in NiFe/Cu/NiFe and Co/Cu/Co tri-layered nanowires. The thermal conductivity and its spin dependence for the tri-layered wires have been evaluated by using an integrated nano-sized thermo couple. We find that the thermal spin-valve effect is always approximately 8 times larger than the electrical spin-valve effect, namely giant magnetoresistance effect. The numerical simulation with the experimental results enable us to estimate the thermal conductivity for the tri-layered wire and its spin dependence. Surprisingly, the spin dependence of the thermal conductivity for the Co/Cu/Co wire is as high as 8%, which is much larger than the electrical one. This indicates a high potential application of the thermal spin-valve effect.

  • Bolometric ferromagnetic resonance techniques for characterising spin-Hall effect at high temperatures

    Phu P., Yamanoi K., Ohnishi K., Hyodo J., Rogdakis K., Yamazaki Y., Kimura T., Kurebayashi H.

    Journal of Magnetism and Magnetic Materials (Journal of Magnetism and Magnetic Materials)  485   304 - 307 2019.09

    ISSN  03048853

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    © 2019 We report on current-induced ferromagnetic resonance techniques to characterise spin-Hall effect at high temperatures. A microwave current was injected into a patterned CoFeB/Pt bi-layer grown on a glass substrate, simultaneously exerting spin-transfer torques through the spin-Hall effect and also causing Joule heating enabling the control of the device temperature. We measured the device temperature by using the device itself as a local temperature sensor. A clear reduction of CoFeB magnetisation was observed as the device temperature was increased allowing us to estimate the Curie temperature of our CoFeB film to be 920 K. The spin-Hall angle of Pt was quantified as (1.72 ± 0.03) × 10−2 at 300 K and was slightly increased to (1.75 ± 0.02) × 10−2 at 410 K. This simple method can be widely used for quantifying the spin-Hall angle of a large variety of materials at high temperatures.

  • Tunable magnetization dynamics in artificial spin ice via shape anisotropy modification

    Dion T., Arroo D.M., Yamanoi K., Kimura T., Gartside J.C., Cohen L.F., Kurebayashi H., Branford W.R.

    Physical Review B (Physical Review B)  100 ( 5 )  2019.08

    ISSN  24699950

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    © 2019 American Physical Society. ©2019 American Physical Society. Ferromagnetic resonance (FMR) is performed on kagome artificial spin ice (ASI) formed of disconnected Ni80Fe20 nanowires. Here we break the threefold angular symmetry of the kagome lattice by altering the coercive field of each sublattice via shape anisotropy modification. This allows for distinct high-frequency responses when a magnetic field is aligned along each sublattice and additionally enables simultaneous spin-wave resonances to be excited in all nanowire sublattices, unachievable in conventional kagome ASI. The different coercive field of each sublattice allows selective magnetic switching via global field, unlocking novel microstates inaccessible in homogeneous-nanowire ASI. The distinct spin-wave spectra of these states are detected experimentally via FMR and linked to underlying microstates using micromagnetic simulation.

  • Modification of the magnetization dynamics of a NiFe nanodot due to thermal spin injection

    Asam N., Yamanoi K., Kimura T.

    Journal of Physics D: Applied Physics (Journal of Physics D: Applied Physics)  51 ( 22 )  2018.05

    ISSN  00223727

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    © 2018 IOP Publishing Ltd. An array of NiFe nanodots has been prepared on a Cu/CoFeAl film. Since a thermal spin current is expected to be excited owing to a large spin-dependent Seebeck coefficient for the CoFeAl, we investigate the magnetization dynamics of the NiFe dots under the temperature gradient along the vertical direction. By using vector network analyzer measurements, we have demonstrated that the temperature gradient produces modulations of the frequency of ferromagnetic resonance and the linewidth of the resonance spectra. The observed parabolic dependences are well explained by the damping-like and field-like components of spin transfer torque.

Papers, etc., Registered in KOARA 【 Display / hide

Research Projects of Competitive Funds, etc. 【 Display / hide

  • スピン渦度結合を用いた反強磁性スピン注入技術の開発


    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Research Activity Start-up , Principal investigator


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