KEIO RESEARCHERS INFORMATION SYSTEM

Other Affiliation 【 Display / hide 】

Other Affiliation 【 Display / hide 】

• 理学部・物理学科, 助教

Career 【 Display / hide 】

Career 【 Display / hide 】

• 2017.04

  -

  2018.03

  Faculty of Sciences Department of Physics, Kyushu University , Post-doctoral fellow

• 2018.04

  -

  2018.06

  九州大学　理学研究院物理学部門, 技術職員

• 2018.07

  -

  2019.03

  University College of London, London Centre for Nanotechnology,  Postdoctoral Research Associate

• 2019.04

  -

  Present

  Keio University, Faculty of Science and Technology Department of Physics, Assistant Professor

Academic Background 【 Display / hide 】

Academic Background 【 Display / hide 】

• 2008.04

  -

  2012.03

  Fukuoka University, 理学部, 応用物理学科

  University, Graduated, Other

• 2012.04

  -

  2014.03

  Fukuoka University, 理学研究科, 応用物理学専攻

  Graduate School, Completed, Master's course

• 2014.04

  -

  2017.03

  Kyushu University, 理学府, 物理学専攻

  Graduate School, Completed, Doctoral course

Academic Degrees 【 Display / hide 】

Academic Degrees 【 Display / hide 】

• Doctor of Science, Kyushu University, National Institution for Academic Degrees and University Evaluation, 2017.03

Research Areas 【 Display / hide 】

Research Areas 【 Display / hide 】

• Natural Science / Magnetism, superconductivity and strongly correlated systems (spintronics, spin dynamics, spin wave, )

Research Keywords 【 Display / hide 】

Research Keywords 【 Display / hide 】

• スピントロニクス、スピンダイナミクス、磁気相転移、音波、ナノテクノロジー

Research Themes 【 Display / hide 】

Research Themes 【 Display / hide 】

• Study on magnon-phonon coupling using sound wave, 

  2019.04

  -

  Present

• Modulation of spintronics effects using magnetic phase transitions, 

  2019.04

  -

  Present

• Study on interplay between heat and spin dynamics in ferromagnetic metal, 

  2014.04

  -

  Present

Papers 【 Display / hide 】

Papers 【 Display / hide 】

• Electric‐Field Control of Low Damping Constant in Epitaxial Co2FeSi/LiNbO3 Multiferroic Heterostructures

  Shinya Yamada, Takamasa Usami, Sachio Komori, Yoshio Miura, Kazuto Yamanoi, Yukio Nozaki, Tomoyasu Taniyama, Kohei Hamaya

  Advanced Science 12 ( 41 )  2025.11

  　View Summary

  To develop electric-field control of magnetization dynamics in a magnetic material for magnonic devices with low-energy power consumption operation, an epitaxial half-metallic Co<inf>2</inf>FeSi/LiNbO<inf>3</inf> multiferroic heterostructure is experimentally demonstrated. The epitaxial Co<inf>2</inf>FeSi/LiNbO<inf>3</inf> multiferroic heterostructure shows a low damping constant (α) of ∼0.006 and the value of α is decreased to ∼0.004 by applying an electric field. This means that the magnetization dynamics in an epitaxial half-metallic Co<inf>2</inf>FeSi layer can be controlled via the piezoelectric strain of LiNbO<inf>3</inf> through the magnetoelastic coupling. This study leads to a way toward the realization of magnonic devices with low-energy power consumption operation.

  • Access to Document (DOI)

• Nanometer-Thick Si/Al Gradient Materials for Spin Torque Generation

  Taisuke Horaguchi, Cong He, Zhenchao Wen, Hayato Nakayama, Tadakatsu Ohkubo, Seiji Mitani, Hiroaki Sukegawa, Junji Fujimoto, Kazuto Yamanoi, Mamoru Matsuo, Yukio Nozaki

  Science Advances 11 ( 19 )  2025.05

  Accepted

  　View Summary

  Green materials for efficient charge-to-spin conversion are desired for common spintronic applications. Recent studies have documented the efficient generation of spin torque using spin-orbit interactions (SOIs); however, SOI use relies on the employment of rare metals such as platinum. Here, we demonstrate that a nanometer-thick gradient from silicon to aluminum, which consists of readily available elements from earth resources, can produce a spin torque as large as that of platinum despite the weak SOI of these compositions. The spin torque efficiency can be improved by decreasing the thickness of the gradient, while a sharp interface was not found to increase the spin torque. Moreover, the electric conductivity of the gradient material can be up to twice as large as that of platinum, which provides a way to reduce Joule heating losses in spintronic devices.

  • Access to Document (DOI)

• Reversal of Spin‐Torque Polarity with Inverting Current Vorticity in Composition‐Graded Layer at the Ti/W Interface

  Hayato Nakayama, Taisuke Horaguchi, Jun Uzuhashi, Cong He, Hiroaki Sukegawa, Tadakatsu Ohkubo, Seiji Mitani, Kazuto Yamanoi, Yukio Nozaki

  Advanced Electronic Materials 11 ( 7 )  2025.05

  ISSN  2199-160X

  　View Summary

  While compositional gradient-induced spin-current generation is explored, its microscopic mechanisms remain poorly understood. Here, the contribution of polarity of compositional gradient on spin-current generation is explored. A nanoscale compositional gradient, formed by in situ atomic diffusion of ultrathin Ti and W layers, is introduced between 10-nm-thick W and Ti layers. Spin-torque ferromagnetic resonance in ferromagnetic Ni<inf>95</inf>Cu<inf>5</inf> deposited on this gradient reveals that a moderate compositional gradient suppresses negative spin torque from the spin Hall effect in W. In contrast, reversing the Ti/W stacking order, which inverts the gradient, suppresses positive spin torque from the orbital Hall effect in Ti. These findings suggest that the sign of spin torque is governed by the polarity of compositional gradient, providing a novel strategy for efficient spin-torque generation without relying on materials with strong spin or orbital Hall effect.

  • Access to Document (DOI)

• Gyro-spintronic material science using vorticity gradient in solids

  Yukio Nozaki, Hiroaki Sukegawa, Shinichi Watanabe, Seiji Yunoki, Taisuke Horaguchi, Hayato Nakayama, Kazuto Yamanoi, Zhenchao Wen, Cong He, Jieyuan Song, Tadakatsu Ohkubo, Seiji Mitani, Kazuki Maezawa, Daichi Nishikawa, Shun Fujii, Mamoru Matsuo, Junji Fujimoto, Sadamichi Maekawa

  Science and Technology of Advanced Materials 26 ( 1 )  2025.02

  Accepted,  ISSN  1468-6996

  　View Summary

  We present a novel method for generating spin currents using the gyromagnetic effect, a phenomenon discovered over a century ago. This effect, crucial for understanding the origins of magnetism, enables the coupling between various macroscopic rotational motions and electron spins. While higher rotational speeds intensify the effect, conventional mechanical rotations, typically, below 10,000 RPM, produce negligible results comparable to geomagnetic fluctuations, limiting applied research. Our studies demonstrate that spin current generation comparable to that of rare metals can be achieved through atomic rotations induced by GHz-range surface acoustic waves and the rotational motion of conduction electrons in metallic thin films with nanoscale gradient modulation of electrical conductivity. These effects, termed the acoustic gyromagnetic effect and the current-vorticity gyromagnetic effect, are significant in different contexts. The acoustic gyromagnetic effect is notable in high-conductivity materials like aluminum and copper, which are more abundant than conventional spintronics materials with strong spin–orbit interactions (SOIs). Conversely, the current-vorticity gyromagnetic effect requires a large conductivity gradient to produce current vorticity efficiently. This is achieved by using composition gradient structures from highly conductive metals to poorly conductive oxides or semiconductors. Consequently, unlike traditional strong-SOI materials, we can create highly efficient spin current generators with low energy dissipation due to reduced Joule loss.

  • Access to Document (DOI)

• Spatiotemporal visualization of a surface acoustic wave coupled to magnons across a submillimeter-long sample by pulsed laser interferometry

  Maezawa K, Fujii S, Yamanoi K, Nozaki Y, Watanabe S

  Physical Review Applied (AMER PHYSICAL SOC)  21 ( 4 )  2024.04

  Research paper (scientific journal), Joint Work,  ISSN  2331-7019

  　View Summary

  Surface acoustic waves (SAWs) coupled to magnons have attracted much attention because they allow for the long-range transport of magnetic information that cannot be achieved by magnon alone. We employed pulsed laser interferometry to visualize the entire spatiotemporal dynamics of a SAW that travels on a nickel (Ni) thin film and is coupled to magnons. It was possible to trace the coupling-induced amplitude reduction and phase shift that occurs as the SAW propagates over a distance of 0.4 mm. The observed changes are consistent with results obtained from conventional radio-frequency transmission measurements, which probe the total SAW absorption due to magnon-phonon coupling. This result verifies that our method can accurately capture the spatiotemporal dynamics of a SAW coupled to magnons across the entire length of the sample. Additionally, we validated our time-resolved profiles by comparing them with theoretical results that take the echo wave due to reflection into account. The impact of the echo wave is significant even when it has propagated over a distance of the order of millimeters. Our imaging results highlight the visualization of the long-range propagation of the SAW coupled to magnons and offer more information about the surface vibration profiles in such devices.

  • Access to Document (DOI)

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

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

• Spin injection in antiferromagnet using spin vorticity coupling

  Yamanoi, Kazuto

  科学研究費補助金研究成果報告書 2020

• Development of thermo-spin energy conversion using surface acoustic wave

  Yamanoi, Kazuto

  学事振興資金研究成果実績報告書 (慶應義塾大学)  2019

Reviews, Commentaries, etc. 【 Display / hide 】

Reviews, Commentaries, etc. 【 Display / hide 】

• Dependence of current-induced switching threshold on composition gradient width in Si/Al-integrated perpendicular magnetic films

  AIP Advances  2026.03

  • Access to Document (DOI)

Presentations 【 Display / hide 】

Presentations 【 Display / hide 】

• Acoustically Driven Magnon-Phonon Coupling in an Epitaxially Grown Co2FeSi Alloy

  Kazuto Yamanoi, Shinya Yamada, Kohei Hamaya, Yukio Nozaki

  [International presentation]  The 8th International Conference on Electronic Materials and Nanotechnology for Green Environment (ENGE2024), 

  2024.11

  , 

  Oral presentation (general)

• Comparison of temperature dependence of the acoustically excited spin waves between NiFe and NiFe/Pt films

  K. Yamanoi, Y. Nozaki

  [International presentation]  International conference on Magnetism 2024, 

  2024.06

  -

  2024.07

  , 

  Poster presentation

• Experimental demonstration of SOT switching in a Pt/Co/Pt trilayer film fabricated on a Si/Al gradient material

  S. Takagi, T. Horaguchi, K. Yamanoi, Y. Nozaki

  [International presentation]  International conference on Magnetism 2024, 

  2024.06

  -

  2024.07

  , 

  Poster presentation

• Direct imaging of spatial decay profiles of surface acoustic waves due to magnon-phonon coupling in ferromagnets

  K. Maezawa, S. Fujii, K. Yamanoi, Y. Nozaki, S. Watanabe

  [International presentation]  International conference on Magnetism 2024, 

  2024.06

  -

  2024.07

  , 

  Oral presentation (general)

• Spin torque modulation using compositional gradient interface between Ti and W

  H. Nakayama, T. Horaguchi, C. He, H. Sukegawa, T. Ohkubo, S. Mitani, K. Yamanoi, Y. Nozaki

  [International presentation]  International conference on Magnetism 2024, 

  2024.06

  -

  2024.07

  , 

  Poster presentation

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

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

• 金属ナノドットハニカム格子のバレー自由度を用いたスピンメカトロニクス

  2025.04

  -

  2028.03

  基盤研究(C), Principal investigator

• キメラ準粒子の高効率生成に向けたメタマテリアル共振器の開発

  2025.04

  -

  2027.03

  学術変革領域研究(A), Principal investigator

• 弾性波を用いた巨大スピンホール効果の起源解明と高効率化に関する研究

  2022

  -

  2023

  公益財団法人 村田学術振興, 公益財団法人 村田学術振興 研究助成, Other, No Setting

• Spin injection in antiferromagnet using spin vorticity coupling

  2019.08

  -

  2021.03

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

  　View Summary

  In this research, we have study a non-thermal spin injection in antiferromagnetic Dy using spin-vorticity coupling(SVC).
  (a)We succeeded the fabricate for a high-quality Dy film by optimizing the deposition conditions. (b)We demonstrated the non-linear change of the spin-pumping effect in a Dy/NiFe bi-layer using a temperature-induced magnetic phase transition of Dy.(c)Since the surface acoustic wave was suppressed by Dy film, the SVC could not be observed. As a solution to these problems, we succeeded in a thinner Dy film.

• 静水圧力による純スピン流制御

  2017

  QRプログラム・わかばチャレンジ, Coinvestigator(s)

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Intellectual Property Rights, etc. 【 Display / hide 】

Intellectual Property Rights, etc. 【 Display / hide 】

• スピントロニクス素子、ワイヤレス給電装置、磁気センサー、磁気記録媒体、磁気メモリ、高周波フィルタおよびスピン発振器

  Date applied： 特願2015-185269  2015.09 

  Date announced： 特開2016-066796  2016.04 

  Patent

Awards 【 Display / hide 】

Awards 【 Display / hide 】

• 学会活動貢献賞

  2025.07, 公益社団法人・日本磁気学会, 企画委員会活動を通した学会活動の活性化への貢献

• 電気学会 令和5年(2023)優秀論文発表賞A(本部表彰)

  2024.09, 一般社団法人電気学会

  Type of Award： Award from Japanese society, conference, symposium, etc.

• 電気学会 令和5年(2023)優秀論文発表賞A(本部表彰)

  山野井一人, 2024.09, 一般社団法人電気学会

• 電気学会 令和3年(2021)優秀論文発表賞(A部門賞)

  山野井一人, 2022.09, 一般社団法人電気学会

  Type of Award： Award from Japanese society, conference, symposium, etc.

• 日本磁気学会　桜井講演賞

  2016.09, 日本磁気学会, 強磁性共鳴による磁性体加熱効果と熱スピン注入

  Type of Award： Award from Japanese society, conference, symposium, etc.

Courses Taught 【 Display / hide 】

Courses Taught 【 Display / hide 】

• PHYSICS LABORATORIES 2

  2025

• PHYSICS LABORATORIES 1

  2025

• PHYSICS D

  2025

• LITERATURE OF PHYSICS

  2025

• LABORATORIES IN SCIENCE AND TECHNOLOGY

  2025

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Courses Previously Taught 【 Display / hide 】

Courses Previously Taught 【 Display / hide 】

• PHYSICS LABORATORIES 1

  Keio University

  2024.04

  -

  2025.03

• PHYSICS LABORATORIES 2

  Keio University

  2024.04

  -

  2025.03

• PHYSICS D

  Keio University

  2024.04

  -

  2025.03

• LABORATORIES IN SCIENCE AND TECHNOLOGY

  Keio University

  2024.04

  -

  2025.03

• PHYSICS LABORATORIES 1

  Keio University

  2023.04

  -

  2024.03

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Media Coverage 【 Display / hide 】

Media Coverage 【 Display / hide 】

• マイクロ波を用いた熱スピン注入技術の開発 －ワイヤレス・スピンデバイスの実現に期待－

  2017.12

• 小さな磁石の大きな可能性

  2016.08

Memberships in Academic Societies 【 Display / hide 】

Memberships in Academic Societies 【 Display / hide 】

• The Institute of Electrical Engineers of Japan, 

  2019.06

  -

  Present

• 日本磁気学会, 

  2016.04

  -

  Present

• 日本物理学会, 

  2013.04

  -

  Present

• 日本応用物理学会, 

  2013.04

  -

  Present

Committee Experiences 【 Display / hide 】

Committee Experiences 【 Display / hide 】

• 2023.06

  -

  Present

  日本磁気学会 企画幹事

• 2023.04

  -

  Present

  日本磁気学会サマースクール, チーフオーガナイザ , 日本磁気学会

• 2023

  -

  Present

  企画幹事, 日本磁気学会

• 2023

  -

  Present

  チーフオーガナイザ, 日本磁気学会サマースクール

• 2021.06

  -

  Present

  日本磁気学会 企画委員 , 日本磁気学会

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