KIKUCHI Nobuaki

写真a

Affiliation

Graduate School of Engineering Science  Department of Mathematical Science and Electrical-Electronic-Computer Engineering  Electrical and Electronic Engineering Course 

To the head of this page.▲

Research Interests 【 display / non-display 】

  • Magnetic Materials

To the head of this page.▲

Graduate School 【 display / non-display 】

  • 　
    -
    2023.03

    Tohoku University  Graduate School,Division of Engineering  Doctor's Course  Completed

To the head of this page.▲

Campus Career 【 display / non-display 】

  • 2024.04
    -
    Now

    Akita University   Graduate School of Engineering Science   Department of Mathematical Science and Electrical-Electronic-Computer Engineering   Electrical and Electronic Engineering Course   Professor  

To the head of this page.▲

External Career 【 display / non-display 】

  • 2024.04
    　
    　

    Akita University   Graduate school of Engineering Sciences   Professor  

  • 2020.10
    -
    2024.03

    Tohoku University   Institute of Multidisciplinary Research for Advanced Materials   Associate Professor  

  • 2007.07
    -
    2020.09

    Tohoku University   Institute of Multidisciplinary Research for Advanced Materials   Assistant Professor  

To the head of this page.▲

Research Areas 【 display / non-display 】

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Electric and electronic materials

  • Nanotechnology/Materials / Applied condensed matter physics

  • Nanotechnology/Materials / Thin film/surface and interfacial physical properties

To the head of this page.▲
 

Research Achievements 【 display / non-display 】

    ◆Original paper【 display / non-display 】

  • Clustering First-order reversal curve diagram using the Gaussian mixture model and the Davies-Bouldin index

    Ying R, T. Taniguchi, K. Nabeta, K. Ishigami, N. Kikuchi, S. Okamoto

    Japanese Journal of Applied Physics ( IOP )  63 ( 11 ) 11SP04   2024.11  [Refereed]

    Research paper (journal)   Domestic Co-author

    Abstract

    In our energy-consuming society, understanding magnetization reversal in permanent magnets is crucial for improving energy conversion efficiency between electric energy and mechanical energy. First-order reversal curves (FORCs) have enabled qualitative studies of reversal mechanisms, however, further understanding based on quantitative analysis is still difficult due to the complexity of FORC diagrams. We introduce a machine-learning based approach combining the Gaussian mixture model and the Davies-Bouldin index to separate characteristic features in FORC diagrams of Nd-Fe-B magnets. The clustering method is evaluated using several FORC diagrams obtained at different temperatures, and we also demonstrated hysteresis loop reconstruction using the clustered FORC diagrams.

    DOI

  • Spin-Current-Driven Permeability Variation for Time-Varying Magnetic Metamaterials

    Toshiyuki Kodama, Nobuaki Kikuchi, Satoshi Okamoto, Seigo Ohno, Satoshi Tomita

    Physical Review Applied ( American Physical Society (APS) )  19 ( 4 )   2023.04  [Refereed]

    Research paper (journal)   Domestic Co-author

    DOI

  • Co-planar waveguide ferromagnetic resonance spectroscopy of cobalt/platinum superlattice metamaterials

    Satoshi Tomita, Nobuaki Kikuchi, Satoshi Okamoto

    Japanese Journal of Applied Physics ( IOP Publishing )  62 ( SB ) SB1010 - SB1010   2023.03  [Refereed]

    Research paper (journal)  

    Abstract

    We study cobalt/platinum (Co/Pt) superlattices by means of ferromagnetic resonance spectroscopy in the frequency domain. The magnetization easy-axis of superlattices, which lies in a plane of the film with Co layers of 1.5 and 1.2 nm thickness, changes to the direction perpendicular to the film surface with Co layers of 0.9 and 0.6 nm thickness. As the Co layer thickness decreases from 0.9 to 0.6 nm, the Gilbert damping parameter significantly increases while the g-value is almost constant. As the Pt layer thickness decreases from 0.6 to 0.3 nm in the superlattices with 0.9 nm thick Co layers, the damping parameter slightly decreases. The present study demonstrates that the Co/Pt superlattices with 0.9 nm thick Co layers and 0.3 nm thick Pt layers are suitable for time-varying magnetic metamaterials realizing a larger magnetic permeability modulation.

    DOI

  • Microwave-assisted switching in granular media with continuous magnetic overlayers for interaction control

    Nobuaki Kikuchi, Katsunari Sato, Takehito Shimatsu, Satoshi Okamoto

    Japanese Journal of Applied Physics ( IOP Publishing )  62 ( SB ) SB1015 - SB1015   2023.03  [Refereed]

    Research paper (journal)   Domestic Co-author

    Abstract

    Optimizing switching behavior under a microwave field is a key issue for microwave-assisted magnetic recording. We study the effect of inter-grain exchange coupling induced by a continuous magnetic layer on microwave-assisted switching of CoCrPt-SiO<sub>2</sub> granular media. The microwave assistance effect is improved in the low-frequency region by introducing the inter-grain exchange coupling, but the coupling reduces the critical frequency. The maximum assistance effect is almost independent of the film structure since the dual effect cancels each other. Micromagnetic simulations also show similar results on exchange coupling between grains. These results indicate that the inter-grain exchange coupling can be used to optimize the critical frequency of the media in practical applications.

    DOI

  • Thermal activation on microwave-assisted magnetization switching in Co/Pt nanodot arrays

    Satoshi Mizutani, Nobuaki Kikuchi, Masatoshi Hatayama, Takehito Shimatsu, Satoshi Okamoto

    Japanese Journal of Applied Physics ( IOP Publishing )  62 ( SB ) SB1012 - SB1012   2023.03  [Refereed]

    Research paper (journal)   Domestic Co-author

    Abstract

    The magnetization switching field is efficiently reduced by exciting precession with a microwave field of GHz frequency. Analytical calculations based on the Landau–Lifshitz–Gilbert equation have revealed that the effect of the thermal activation process plays an important role in magnetization switching behavior under a microwave field. In this study, we experimentally investigated the microwave-assisted magnetization switching (MAS) behavior of Co/Pt nanodot arrays under various microwave field conditions. Experimental results were compared with the calculated effective energy barrier height of MAS. Consequently, all the experimental MAS behaviors can be explained by the effect of thermal activation, but quantitative discussion will require accurate experimental studies.

    DOI

    • display all >>

    To the head of this page.▲

    ◆Introduction and explanation【 display / non-display 】

  • Microwave Assisted Magnetization Switching

      15 ( 2 ) 89 - 95   2020.04

    Introduction and explanation (scientific journal)  

  • First-order Reversal Curve (FORC) Analysis and Its Application for Permanent Magnet Materials

    Okamoto S., Yomogita T., Miyazawa K., Kikuchi N., Kitakami O., Watanabe N., Suita N.

    Materia Japan ( The Japan Institute of Metals and Materials )  56 ( 9 ) 533 - 540   2017

    Introduction and explanation (others)  

    1521

    DOI

    • To the head of this page.▲

    ◆International conference proceedings【 display / non-display 】

  • Effect of film thickness on microwave assisted switching behavior

    Nobuaki Kikuchi, Katsunari Sato, Masatoshi Hatayama, Takehito Shimatsu, Satoshi Okamoto

    2023 IEEE International Magnetic Conference - Short Papers (INTERMAG Short Papers) ( IEEE )    2023.05

    Research paper (international conference proceedings)  

    DOI

  • MICROWAVE ASSISTED SWITCHING BEHAVIOR OF COCRPT BASED GRANULAR MEDIA

    Nobuaki KIKUCHI, Kyohei SHIMADA, Shun KIKUCHI, Katsunari SATO, Satoshi OKAMOTO, Osamu KITAKAMI, Takehito SHIMATSU

    Digest of the 29th Magnetic Recording Conference 2018(TMRC2018)     41 - 42   2018.08

    Research paper (international conference proceedings)  

  • Tuning Magnetic Anisotropy and Curie Temperature of L1<SUB>0</SUB>-FePt Granular films

    T. Shimatsu, T. Ono, T. Moriya, H. Nakata, K. Komiyama, S. Uchida, H. Oyama, H. Kikuchi, H. Kataoka, K. Sato, A. Furuta, T. Yoshizawa, M. Hatayama, K. Tsumura, N. Kikuchi, O. Kitakami

    Digest of the 28th Magnetic Recording Conference 2017(TMRC2017)     2017.08  [Invited]

    Research paper (international conference proceedings)  

    Tsukuba, August(2017) A-1

    • To the head of this page.▲

    ◆University bulletin, Research institution【 display / non-display 】

  • 双極子結合した積層磁性ドットによるマイクロ波アシスト実験

    金原大樹, 岡本聡, 菊池伸明, 北上修, 島津武仁

    電気学会研究会資料   MAGZ43 ( 234 ) 21 - 25   2017.11

    Research paper (university bulletin, research institution)  

    562

  • 双極子結合した積層磁性ドットによるマイクロ波アシス化反転

    金原大樹, 岡本聡, 菊池伸明, 北上修, 島津武仁

    電子情報通信学会 信学技報   MR2017-8   53 - 58   2017.08

    Research paper (university bulletin, research institution)  

    560

    • To the head of this page.▲

    ◆Other【 display / non-display 】

  • Nonlinear Effect of Spin-Torque Ferromagnetic Resonance in Py/Pt Bilayers

    児玉俊之, 菊池伸明, 千葉貴裕, 岡本聡, 岡本聡, 大野誠吾, 冨田知志, 冨田知志

    応用物理学会秋季学術講演会講演予稿集(CD-ROM)   84th   2023

    J-GLOBAL

  • Spin-current Induced Permeability Control of NiFe Wires towards Time-varying Metamaterials

    児玉俊之, 菊池伸明, 岡本聡, 岡本聡, 大野誠吾, 冨田知志, 冨田知志

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   70th   2023

    J-GLOBAL

  • Spin-injection Induced Permeability Control for Time-varying Metamaterials

    児玉俊之, 清水蓮也, 菊池伸明, 岡本聡, 岡本聡, 大野誠吾, 冨田知志, 冨田知志

    日本磁気学会学術講演概要集   47th   2023

    J-GLOBAL

  • Permeability Control of Co Wires by Spin-current Injection for Time-varying Metamaterials

    清水蓮也, 児玉俊之, 菊池伸明, 岡本聡, 岡本聡, 大野誠吾, 冨田知志, 冨田知志

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   70th   2023

    J-GLOBAL

  • Permeability control for time-varying metamaterials

      MAG22146   2022.11

    Summary of the papers read (national conference and other science council)  

    • display all >>

To the head of this page.▲

Grant-in-Aid for Scientific Research 【 display / non-display 】

  • Research of synthetic antiferromagnet for THz devices with Brillouin light scattering

    Grant-in-Aid for Scientific Research(B)

    Project Year： 2021.04  -  2024.03 

  • Energy loss analysis in soft magnetic particles for high frequency region and development of its design method

    Grant-in-Aid for Scientific Research(B)

    Project Year： 2020.04  -  2023.03  Investigator(s): Satoshi Okamoto

  • Feasibility study on multilevel memory based on skyrmion dynamics

    Grant-in-Aid for Challenging Research (Exploratory)

    Project Year： 2017.06  -  2019.03  Investigator(s): Okamoto Satoshi, Sato Rie

  • Generation of circularly polarized femtosecond coherent soft x-rays and its application to ultrafast spin dynamics

    Grant-in-Aid for Scientific Research(A)

    Project Year： 2017.04  -  2021.03  Investigator(s): Takahashi Eiji

  • Engineering technology for high frequency spin dynamics

    Grant-in-Aid for Scientific Research(B)

    Project Year： 2017.04  -  2020.03  Investigator(s): Okamoto Satoshi

display all >>

To the head of this page.▲

Presentations 【 display / non-display 】

  • Nonlinear Variation in Permeability Towards Time-varying Metamaterials

    T. Kodama, N. Kikuchi, T. Chiba, S. Okamoto, S. Ohno, S. Tomita

    Metamaterials 2024  2024.09  -  2024.09 

  • Towards time-varying magnetic metamaterials

    Toshiyuki Kodama, Nobuaki Kikuchi, Satoshi Okamoto, Seigo Ohno, Satoshi Tomita  [Invited]

    The 8th A3 Metamaterials Forum  2024.07  -  2024.07 

  • Observation of Current-induced Nonlinear Spin Torque in Pt-Py Bilayers

    Toshiyuki Kodama, Nobuaki Kikuchi, Takahiro Chiba, Satoshi Okamoto, Seigo Ohno, Satoshi Tomita

    The 22nd International Conference on Magnetism  2024.07  -  2024.07 

  • Effect of film thickness on microwave assisted switching behavior

    N. Kikuchi, K. Sato, M. Hatayama, T. Shimatsu, S. Okamoto

    INTERMAG 2023  2023.05  -  2023.05 

  • Spin-current Driven Magnetic Meta-atoms for Time- Varying Permeability

    R. Shimizu, T. Kodama, N. Kikuchi, S. Okamoto, S. Ohno, S. Tomita

    INTERMAG 2023  2023.05  -  2023.05 

display all >>

To the head of this page.▲
 

Academic Activity 【 display / non-display 】

  • 2024.04
    -
    2024.09

  • 2023.04
    -
    Now

  • 2023.03
    -
    Now

  • 2022.06
    -
    Now

To the head of this page.▲