SEKIGUCHI Koji

Affiliation

Faculty of Engineering, Division of Intelligent Systems Engineering

Job Title

Professor

Research Fields, Keywords

spintronics, Brillouin light scattering, magnonics, magnetism


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The Best Research Achievement in Research Career 【 display / non-display 】

  • 【Published Thesis】 Time-domain Measurement of Current-induced Spin Wave Dynamics  2011.01

    【Awards】 文部科学大臣表彰若手科学者賞  2015.04

    【Published Thesis】 Spin Wave Propagation in Cubic Anisotropy Materials  2017.06

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Degree 【 display / non-display 】

  • Doctor of Science - Keio University

  • Master of Science - Keio University

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Campus Career 【 display / non-display 】

  • 2021.4
    　
    　

    Duty   Yokohama National UniversityFaculty of Engineering   Division of Intelligent Systems Engineering   Professor  

  • 2018.4
    -
    2021.3

    Duty   Yokohama National UniversityFaculty of Engineering   Division of Intelligent Systems Engineering   Associate Professor  

  • 2023.4
    　
    　

    Concurrently   Yokohama National UniversityInstitute of Advanced Sciences   Professor  

  • 2021.4
    　
    　

    Concurrently   Yokohama National UniversityGraduate school of Engineering Science   Department of Mathematics, Physics, Electrical Engineering and Computer Science   Professor  

  • 2021.4
    　
    　

    Concurrently   Yokohama National UniversityGraduate School of Engineering   Department o Physics, Electrical and Computer Engineering   Professor  

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Books 【 display / non-display 】

  • スピン波ドップラー効果とマグノン制御

    （ Role： Sole author）

    応用物理学会 

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    Language：Japanese Book type：Scholarly book

    応用物理83巻3号

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Thesis for a degree 【 display / non-display 】

  • ナノスケール強磁性体におけるスピン依存量子伝導機構の研究

    関口 康爾

    2007.3

    Doctoral Thesis   Single Work    [Reviewed]

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    ナノスケール強磁性体におけるスピン自由度に依存した電気伝導量子化が生じること、Aharonov-Bohm効果にスピン依存効果が出ることを示した。

  • 強磁性極微細線におけるスピン依存量子伝導

    関口 康爾

    2004.3

    Master Thesis   Single Work    [Reviewed]

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    原子スケールの強磁性細線では、電気伝導度がスピンに依存して量子化すること、巨大な磁気抵抗効果が出現することを明らかにした。

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Papers 【 display / non-display 】

  • Magnetic field detection with single mode spin wave interference in asymmetric structure

    Nishitani, Y; Kaneko, Y; Sekiguchi, K

    SCIENTIFIC REPORTS   15 ( 1 )   2025.2

    DOI Web of Science PubMed

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    Language：English   Publishing type：Research paper (scientific journal)   Joint Work  

  • Frequency-dependent breakdown of backward volume spin-wave soliton formation

    Iwata, T; Nezu, S; Sekiguchi, K

    APPLIED PHYSICS LETTERS   125 ( 22 )   2024.11

    DOI Web of Science

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    Language：English   Publishing type：Research paper (scientific journal)   Joint Work  

  • Frequency-dependent breakdown of backward volume spin-wave soliton formation

    Iwata Tokiya, Nezu Shoki, Sekiguchi Koji

    Applied Physics Letters   125 ( 22 )   2024.11

    CiNii Research

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing   Joint Work  

    This study investigates the propagation characteristics of spin waves in an yttrium iron garnet waveguide using a vector network analyzer and a real-time oscilloscope. We confirm the propagation of backward volume magnetostatic spin waves in the linear regime. Solitary spin-wave formation was observed, and the transition from linear to nonlinear response was verified by establishing a threshold power. In the nonlinear regime, collision experiments between two spin waves were conducted, revealing a dependence of attenuation on the input carrier frequency. A comparison with the transmission loss curve confirms the correlation between attenuation and the position of “frequency regions with strong dispersion.” Notably, only within a specific frequency range among these regions do the colliding spin waves maintain their shapes and momenta, passing through each other without dissipation. This remarkable phenomenon is crucial for dissipation-free information transfer. Our findings offer valuable insights into spin-wave behavior, particularly for developing spin-wave-based logic and long-distance magnonic soliton information transfer.

  • Magnonic noise in the parametric spin-wave pumping process

    Nishiwaki, Y; Nezu, S; Sekiguchi, K

    JAPANESE JOURNAL OF APPLIED PHYSICS   63 ( 10 )   2024.10

    DOI Web of Science

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    Language：English   Publishing type：Research paper (scientific journal)   Joint Work  

  • Enhanced signal-to-noise ratio in magnonic logic gates via dipole coupling

    Hayashi, R; Nezu, S; Sekiguchi, K

    PHYSICAL REVIEW APPLIED   22 ( 3 )   2024.9  [Reviewed]

    DOI Web of Science

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    Language：English   Publishing type：Research paper (scientific journal)   Joint Work  

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Review Papers 【 display / non-display 】

  • The Basis of Magnon Transistors

    K. Sekiguchi

    AAPPS Bulletin 28, 2 (2018).   2018

    DOI

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    Language：English   Publishing type：Article, review, commentary, editorial, etc. (international conference proceedings)  

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

  • マグノントランジスタによる無配線・電流ゼロコンピューティングへの挑戦

    Grant number：22K18321  2022.4 - 2026.3

    日本学術振興会  Grant-in-Aid for Challenging Research (Pioneering)

    Investigator(s)：関口　康爾

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    Authorship：Principal investigator  Grant type：Competitive

    CPS/IoT社会が生み出す大量の信号を、既存CMOSデバイスで処理するには膨大な負荷がネットワークにかかる。本研究では、電流よりも圧倒的にロスが小さい非電荷キャリア（マグノン）を使った演算素子により、低エネルギーで動作するセンサ近傍での信号処理（エッジコンピューティング）技術に挑戦する。既存のマグノントランジスタ研究に対して、本研究では波動干渉を積極活用した多入力・無配線信号処理を研究し、演算部で電流ゼロを実現する革新的デバイス学術体系を打ち立てる。センサ信号の高精度分類化(高次元化)を処理できるマグノンリザバーを構築し、電流ゼロ・エッジコンピューティングに挑戦する。

  • マグノニック機能創発のための電圧効果と凝縮効果の研究

    2019.4

    科学研究費補助金  Grant-in-Aid for Scientific Research(A)

    Investigator(s)：関口康爾

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    Grant type：Competitive

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Presentations 【 display / non-display 】

  • Magnon transistor for next generation computing (invited)

    K. Sekiguchi  [Invited]

    Magnon transistor for next generation computing  MSJ

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    Event date： 2019.9

    Language：English   Presentation type：Oral presentation (general)  

  • Shape-Forming of Spin Wave Packets by Dynamic Magnonic Crystal

    M. Iwaba, K. Sekiguchi,

    Shape-Forming of Spin Wave Packets by Dynamic Magnonic Crystal  MORSI2019, We-02-2

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    Event date： 2019.6

    Language：English   Presentation type：Oral presentation (general)  

  • Time domain Detection of Multiple Spin-wave Solitons Generation

    M. Kawase, M. Iwaba, and K. Sekiguchi

    Time domain Detection of Multiple Spin-wave Solitons Generation  MORIS2019

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    Event date： 2019.6

    Language：English   Presentation type：Oral presentation (general)  

  • Generation of fast propagating spin-wave for magnonic logic functions

    K. Sekiguchi  [Invited]

    Collaborative Conference on Materials Research (CCMR) 2018, 27June. 2018 (invited)  

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    Event date： 2018.6

    Language：English   Presentation type：Oral presentation (invited, special)  

    K. Sekiguchi, "Generation of fast propagating spin-wave for magnonic logic functions", Collaborative Conference on Materials Research (CCMR) 2018, 27June. 2018 (invited)
    (http://ccmr2018.org/program/)

  • Edge-mode Spin-wave Nonreciprocity for Magnonic Logic Functions

    K. Sekiguchi  [Invited]

    5th International Conference of Asian Union of Magnetics Societies (IcAUMS 2018), G4-1399, 7June. 2018 (invited) 

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    Event date： 2018.6

    Language：English   Presentation type：Oral presentation (invited, special)  

    K. Sekiguchi, "Edge-mode Spin-wave Nonreciprocity for Magnonic Logic Functions", 5th International Conference of Asian Union of Magnetics Societies (IcAUMS 2018), G4-1399, 7June. 2018 (invited)
    (http://www.icaums.org/main/pr_program.htm)

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Charge of on-campus class subject 【 display / non-display 】

  • 2025   Solid-State Electronic Physics

    College of Engineering Science

  • 2025   Semiconductor Engineering

    College of Engineering Science

  • 2025   Laboratory B for Electrical and Computer Engineering

    College of Engineering Science

  • 2025   Laboratory Ⅱ for Electrical and Computer Engineering

    College of Engineering Science

  • 2025   Advanced integrated system design S

    Graduate school of Engineering Science

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