Details of a Researcher - Nozaki, Yukio

Nozaki, Yukio

写真a

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

Position: Professor

Related Websites

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Career 【 Display / hide 】

1998.04

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2006.07

Assistant Professor, ISEE, Kyushu University, システム情報科学研究院, 助手
2006.08

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2010.03

Assoc. Professor, ISEE, Kyushu University, システム情報科学研究院, 准教授
2010.04

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2016.03

Assoc. Professor, Dept. of Physics, Keio University, 理工学部物理学科, 准教授
2016.04

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2017.03

東京大学, 物性研究所, 客員教授
2016.04

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Present

Assoc. Professor, Dept. of Physics, Keio University, 理工学部物理学科, 教授

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Academic Background 【 Display / hide 】

1993.03

Keio University, Faculty of Science and Engineering, Department of Physics

University, Graduated
1995.03

Keio University, Graduate School, Division of Science and Engineering, Department of Physics

Graduate School, Completed, Master's course
1998.03

Keio University, Graduate School, Division of Science and Engineering, Department of Physics

Graduate School, Completed, Doctoral course

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Academic Degrees 【 Display / hide 】

Ph, D, Keio University, Coursework, 1998.03

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Research Areas 【 Display / hide 】

Natural Science / Magnetism, superconductivity and strongly correlated systems (Physical Properties II)

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Research Keywords 【 Display / hide 】

Spin dynamics
Spintronics
Spin Mechatronics
Magnetism
Magnetic device

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Research Themes 【 Display / hide 】

非線形スピンダイナミクスの温度依存性に関する研究,

2016.04

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Present
巨視的回転と微視的スピン角運動量の双方向変換,

2015.04

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Present
チューナブル回転磁場の生成と非線形スピンダイナミクス励起に関する研究,

2015.04

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Present
非平衡状態の非線形ダイナミクスに関する研究,

2014.04

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Present
スピンダイナミクス由来のスピン流によるスピン移行トルクの測定,

2014.04

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Present

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Papers 【 Display / hide 】

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 (Wiley) 2400797-1 - 2400797-9 2025.04

Lead author, Last author, Corresponding author, Accepted, ISSN 2199-160X

　View Summary

Abstract

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<sub>95</sub>Cu<sub>5</sub> 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 (Informa UK Limited) 26 ( 1 ) 2428153-1 - 2428153-39 2025

Accepted, ISSN 14686996

　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

Kazuki Maezawa, Shun Fujii, Kazuto Yamanoi, Yukio Nozaki, Shinichi Watanabe

Physical Review Applied (American Physical Society (APS)) 21 ( 4 ) 044047-1 - 044047-13 2024.04

Accepted

　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)
Enhanced orbital torque efficiency in nonequilibrium Ru50Mo50(0001) alloy epitaxial thin films

Ke Tang, Cong He, Zhenchao Wen, Hiroaki Sukegawa, Tadakatsu Ohkubo, Yukio Nozaki, Seiji Mitani

APL Materials (AIP Publishing) 12 ( 3 ) 031131-1 - 031131-7 2024.03

Accepted

　View Summary

Epitaxial thin films of fully nonequilibrium hcp-Ru50Mo50(0001) nanoalloys were prepared as a chemically disordered alloy, in which the intrinsic spin Hall effect is expected to be negligible. Structural analyses confirmed the epitaxial growth and atomic scale alloying of the films. In contrast to a tiny torque efficiency (ξDL) of ∼0.4% for Ru50Mo50/CoFeB, the ξDL for the Ru50Mo50/Ni heterostructure reached ∼30% with a long-range relaxation length. The apparent dependence of ξDL on the ferromagnetic layer can be attributed to the orbital Hall effect (OHE). Interestingly, a smaller ξDL was observed for Ru/Ni, suggesting that the nonequilibrium Ru50Mo50 enhances its OHE. Furthermore, the enhanced ξDL is maintained by inserting a Ru layer between the Ru50Mo50 and Ni layers, showing orbital transport through Ru. This finding illustrates potential applications of nonequilibrium nanoalloy films in spin orbitronics and contributes to getting insights into the understanding of the interrelationships between nanostructures and orbital transport properties.
- Access to Document (DOI)
Y3Fe5O12 film with multi-domain epitaxy on single-crystalline LiNbO3 substrate

Kazuto Yamanoi, Kenta Hase, Sachio Komori, Tomoyasu Taniyama, Yukio Nozaki

APL Materials (AIP Publishing) 12 ( 2 ) 2024.02

Accepted

　View Summary

Y3Fe5O12 is one of the magnetic insulators that can realize high-speed and low-power-consuming spintronics devices. However, it is hard to prepare a high-quality Y3Fe5O12 film via a conventional sputtering process owing to its low crystalline texture, which leads to a crucial increase in the Gilbert damping constant. Moreover, a single crystalline Gd3Ga5O12 substrate, whose lattice constant is well matched with Y3Fe5O12, is indispensable to improve the crystallinity of the Y3Fe5O12 film. In this article, we demonstrated an epitaxial growth of multiple domains for a 30-nm-thick Y3Fe5O12 film by means of magnetron sputtering on a single crystalline 128° Y–X LiNbO3 substrate , which has been widely utilized in surface acoustic wave devices. From the pole figure of x-ray diffraction, an oblique epitaxial growth of Y3Fe5O12(400) is successfully observed on the 128° Y–X LiNbO3 substrate after a high-temperature post-annealing. The saturation magnetization is equivalent to the value of the epitaxial Y3Fe5O12 film on the Gd3Ga5O12 substrate. The relatively low effective Gilbert damping constant of 0.0039 also supports the high crystalline texture of the Y3Fe5O12 film. The developed growth technique will pave the way for the application of the Y3Fe5O12 film on magneto-acoustic devices.
- Access to Document (DOI)

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

Study on efficient generation of spin current using macroscopic angular momentum

Nozaki, Yukio

科学研究費補助金研究成果報告書 2020
Research on dynamical process of spinwave-assisted magnetization reversal and observation of spinwaves excited along thickness direction

Nozaki, Yukio

科学研究費補助金研究成果報告書 2016
Low power consuming magnetization reversal using electric field coupled spin injector

Nozaki, Yukio

科学研究費補助金研究成果報告書 2014
Research on 3 dimensional magnetic recording for high-capacity and low power consuming storage technologies

Nozaki, Yukio

科学研究費補助金研究成果報告書 2013
Microwave-assisted magnetization reversal of perpendicularly magnetized nanoscale magnetic dot and its applications to nonvolatile memories

Nozaki, Yukio

科学研究費補助金研究成果報告書 2010

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Presentations 【 Display / hide 】

Structural design of surface acoustic wave resonators for enhanced magnon-phonon coupling

A. Nagao, K. Yamanoi, Y. Nozaki

IcAUMS 2025: International Conference of Asian Union of Magnetics Societies,

2025.04
,
Poster presentation
Spin-torque efficiency of Si-Al alloy films with varying compositional ratios and deposition methods

H. Nakayama, T. Horaguchi, K. Yamanoi, Y. Nozaki

IcAUMS 2025: International Conference of Asian Union of Magnetics Societies,

2025.04
,
Oral presentation (general)
Spin-current excitation using ultrafast laser pulses in a heavy-metal/rare-earth iron garnet heterojunction

S. Takahashi, Y. You, K. Yamanoi, Y. Nozaki, T. Satoh, K. T. Yamada

IcAUMS 2025: International Conference of Asian Union of Magnetics Societies,

2025.04
,
Poster presentation
Numerical analysis of dispersion relation and fabrication of magnetic dots in honeycomb Phononic crystals

Y. You, K. Yamanoi, Y. Nozaki

IcAUMS 2025: International Conference of Asian Union of Magnetics Societies,

2025.04
,
Poster presentation
Nonreciprocal spin wave excitation in NixFe1-x alloy induced by surface acoustic waves

S. Sakai, K. Yamanoi, Y. Nozaki

IcAUMS 2025: International Conference of Asian Union of Magnetics Societies,

2025.04
,
Poster presentation

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

Chimera Quasiparticles: Physics

2024.04

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2029.03

学術変革領域研究(A), Principal investigator
Study on the microscopic mechanism of non-adiabatic gyromagnetic effect through crystallographic texture control and manifestation of giant spin torque

2024.04

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2027.03

基盤研究(A), Principal investigator
Study on multi-scale angular momentum conversion and generation of mechanical rotation from electron spin

2021.04

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2024.03

MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A) , Principal investigator
ナノ構造制御と計算科学を融合した傾斜材料開発とスピンデバイス応用

2019.10

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2025.03

JST, CREST, Research grant, Principal investigator
音波を用いたスピン流の高効率生成と伝導制御に関する研究

2018.04

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2021.03

MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A) , Principal investigator

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Intellectual Property Rights, etc. 【 Display / hide 】

スピントロニクスデバイス、磁気メモリ及び電子機器

Date applied： PCT/JP2019/034831 2019.09

Patent, Single
スピントロニクスデバイス、磁気メモリ及び電子機器

Date applied： 2018-165900 2018.09

Patent, Single
静磁気結合を利用した磁性ランダムアクセスメモリセル

Date issued：特許 2003-408344 2011.06

Patent, Joint
磁性多層膜ドットを用いた高周波デバイス

Date issued：特許第4189502

Patent, Joint
磁気メモリ装置及びその書き込み方法

Date announced：特許公開2007－242092

Patent

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Awards 【 Display / hide 】

SRC論文賞2009

NOZAKI Yukio, 2010.06, Microwave-assisted magnetization reversal in a Co/Pd multilayer with perpendicular magnetic anisotropy Applied Physics Letters, Vol. 95, No. 8, Art. No. 082505 (August, 2009).

Type of Award： Award from publisher, newspaper, foundation, etc.
日本磁気学会論文賞

能崎幸雄, 立石健太郎, 白石壮馬, 松山公秀, 2009.09, サブミクロン幅NiFe薄膜パターンのマイクロ波アシスト磁化反転 Journal of Magnetic Society of Japan, Vol. 33, No. 3, pp.208 – 211 (2009)

Type of Award： Award from Japanese society, conference, symposium, etc.
Storage Research Consortium(SRC) 2009年度論文賞

2009.06
日本磁気学会論文賞

2008.09
第1回全学教育優秀授業賞（九州大学）

NOZAKI Yukio, 2007.09

Type of Award： Other