九州大学-研究者情報 [黒川雄一郎 (助教) システム情報科学研究院情報エレクトロニクス部門]

1.	Yuichiro Kurokawa, Yusuke Tahara, Yuki Hamada, Masahiro Fujimoto, Hiromi Yuasa , Scalable spin Seebeck thermoelectric generation using Fe-oxide nanoparticle assembled film on flexible substrate, Scientific Reports, 12, p. 16605, 2022.10.
2.	Yuichiro Kurokawa, Keisuke Yamada, Tomohiro Taniguchi, Shu Horiike, Terumitsu Tanaka, Hiromi Yuasa, Ultra-wide-band millimeter-wave generator using spin torque oscillator with strong interlayer exchange couplings, Scientific Reports, 12, p.10849, 2022.07, Recent increased development interest in millimeter-wave oscillator devices has necessitated realization of small oscillators with high frequency, wide frequency tunability, and room-temperature operation. Spin-torque oscillators (STOs) are fascinating candidates for such applications because of their nanometer size and suitability for room-temperature operation. However, their oscillation frequency and tunable range are limited to the order of 100 MHz–10 GHz. Here, we propose use of bilinear (J1) and biquadratic (J2) interlayer exchange couplings between ferromagnets in STOs to overcome these problems. The bilinear coupling contributes to oscillation frequency enhancement, whereas the biquadratic coupling facilitates frequency tunability via a current. Using micromagnetic simulation with parameters estimated from a material with small saturation magnetization, for J1 = 0 and J2 = − 1.0 mJ/m^2, respectively, we find that the STO exhibits high frequency from 23 to 576 GHz and that its tunability reaches 61 GHz/(10^11 A/m^2) for current densities of − 0.5 to − 9.5 × 10^11 A/m^2. An analytical theory based on the macrospin model is also developed, which exhibits good quantitative agreement with the micromagnetic simulations. These results introduce new possibilities for spintronics applications in high-frequency devices such as next-generation mobile communications..
3.	Shilei Ding, Andrew Ross, Romain Lebrun, Sven Becker, Kyujoon Lee, Isabella Boventer, Souvik Das, Yuichiro Kurokawa, Shruti Gupta, Jinbo Yang, Gerhard Jakob, and Mathias Kläui, Interfacial Dzyaloshinskii-Moriya interaction and chiral magnetic textures in a ferrimagnetic insulator, PHYSICAL REVIEW B, https://doi.org/10.1103/PhysRevB.100.100406, 100, 100406(R), 100, 100406(R) (2019), 2019.09, [URL], The interfacial Dzyaloshinskii-Moriya interaction (DMI) in multilayers of heavy metal and ferromagnetic metals enables the stabilization of novel chiral spin structures such as skyrmions. Magnetic insulators, on the other hand, can exhibit enhanced dynamics and properties such as lower magnetic damping and therefore it is of interest to combine the properties enabled by interfacial DMI with insulating systems. Here, we demonstrate the presence of interfacial DMI in heterostructures that include insulating magnetic layers. We use perpendicularly magnetized insulating thulium iron garnet (TmIG) films capped by the heavy metal platinum, grown on gadolinium gallium garnet (GGG) substrates, and find a surprisingly strong interfacial DMI that, combined with spin-orbit torque, results in efficient switching. The interfacial origin is confirmed through thickness-dependence measurements of the DMI, revealing the characteristic 1/thickness dependence. We combine chiral spin structures and spin-orbit torques for efficient switching and identify skyrmions that allow us to establish the GGG/TmIG interface as the possible origin of the DMI..
4.	Yuichiro Kurokawa, Masakazu Wakae, Satoshi Sumi, Hiroyuki Awano, Kohei Ohnishi, Hiromi Yuasa, Spin-orbit torque-driven current-induced domain wall motion in Gd-Fe magnetic wires, Japanese Journal of Applied Physics, 10.7567/1347-4065/aafa91, 58, 3, 2019.03, [URL], We fabricated Gd-Fe/Ta/sub. and W/Gd-Fe/Ta/sub. perpendicular magnetized magnetic wires and investigated current-induced domain wall motion (CIDWM) in them. The propagation field of the Gd-Fe wires is low (∼3 mT), and the wires were found to have a low threshold current density (∼3.1 ×10¹⁰ A m^-2) of CIDWM. The directions of the CIDWM in Gd-Fe/Ta and W/Gd-Fe/Ta wires are opposite to each other, indicating that the CIDWM in both wires is driven by spin-orbit torque because the spin Hall torque generated by the Ta underlayer and W cap layer oppose each other..
5.	Masakazu Wakae, Yuichiro Kurokawa, Hiromi Yuasa, Observation of spin-orbit torque-induced magnetization switching in Gd-Fe perpendicular magnetized wire with in-plane exchange bias field, Japanese Journal of Applied Physics, 10.7567/1347-4065/aaf877, 58, 2019.01, [URL], We fabricated a Ta/Gd-Fe/Ta and a Ta/Gd-Fe/Ir₂₂Mn₇₈/Co₉₀Fe₁₀/Ta multilayered magnetic wire and investigated spin-orbit torque current-induced magnetization switching in these wires. Magnetization switching in the Ta/Gd-Fe/Ir₂₂Mn₇₈/Co₉₀Fe₁₀/Ta multilayered magnetic wire can be observed by an electric current even if the external in-plane magnetic field is not applied at all. Moreover, we successfully observed the periodical magnetization switching in the Ta/Gd-Fe/Ir₂₂Mn₇₈/Co₉₀Fe₁₀/Ta multilayered magnetic wire in zero magnetic field. This indicates that the present wire is a promising material to realize magnetic random access memory with low power consumption..
6.	Yuichiro Kurokawa, Hiroyuki Awano, Multilayered current-induced domain wall motion in Pt/Tb-Co/Ta/Tb-Co/Pt magnetic wire, AIP ADVANCES, 10.1063/1.5017814, 8, 2, 2018.02, We fabricated a Pt (3 nm)/Tb0.28Co0.72 (4 nm)/Ta (4 nm)/Tb0.26Co0.74 (4 nm)/Pt (3 nm) multilayered magnetic wire and investigated current-induced domain wall motion within it.We found that the Hall resistance of the Pt/Tb-Co/Ta/Tb-Co/Pt wire has four stable levels under a magnetic field of zero. Moreover, we observed that the domain walls in both the upper and lower ferromagnetic layers are controlled by a single current source. This indicates that Pt/Tb-Co/Ta/Tb-Co/Pt wire can be used in multi-level magnetic wire memory..
7.	Yuichiro Kurokawa, Akihiro Shibata, Hiroyuki Awano, Enhancement of spin orbit torques in a Tb-Co alloy magnetic wire by controlling its Tb composition, AIP ADVANCES, 10.1063/1.4974280, 7, 5, 2017.05.
8.	＠Yuichiro Kurokawa, Ryogo Yoshimura, Satoshi Sumi, Hiroyuki Awano, Thermal reduction of the threshold current density for current-induced domain wall motion in Tb-Co magnetic alloy wire, AIP ADVANCES, 10.1063/1.4979727, 7, 3, 2017.03.
9.	Yuichiro Kurokawa, Masaya Kawamoto, Hiroyuki Awano, Current-induced domain wall motion attributed to spin Hall effect and Dzyaloshinsky-Moriya interaction in Pt/GdFeCo (100 nm) magnetic wire, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.55.07MC02, 55, 7, 2016.07.
10.	Yuichiro Kurokawa, Takehiko Hihara, Ikuo Ichinose, Critical field of two-dimensional superconducting Sn_1-x/Si _x bimetallic composite cluster assembled films with energetic cluster impact deposition, Journal of Applied Physics, 10.1063/1.4798262, 113, 17, 2013.05, [URL].

主要学会発表等

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1.	黒川雄一郎、山田啓介、谷口知大、堀池周、田中輝光、湯浅裕美, 低飽和磁化材料をフリー層とするbiquadratic 結合を用いたスピントルクオシレータの基礎検討, 第68回応用物理学会春季学術講演会, 2021.03.
2.	Yuichiro Kurokawa, Masahiro Fujimoto, and Hiromi Yuasa, Investigation of anomalous Nernst effect toward thin flexible temperature sensor, 33th International Microprocesses and Nanotechnology Conference, 2020.11.
3.	伊藤正裕, 若江将和, 黒川雄一郎, 大西紘平, 湯浅裕美, Tb-Gd-Fe細線におけるスピンオービットトルクのTb濃度依存性, 日本物理学会第74回年次大会, 2019.03.
4.	Yuichiro Kurokawa, Masakazu Wakae, Masahiro Itoh, Satoshi Sumi, Hiroyuki Awano, Kohei Ohnishi, Hiromi Yuasa, Investigation of Y-shaped magnetic wire logic device by current-induced domain wall motion, 第66回応用物理学会春季学術講演会, 2019.03.
5.	Masakazu Wakae, Masahiro Itoh, Yuichiro Kurokawa, Kohei Ohnishi, Hiromi Yuasa, Observation of spin-orbit torque magnetization switching in Gd-Fe perpendicular magnetized wire with IrMn cap layer, 第66回応用物理学会春季学術講演会, 2019.03.
6.	鍾永師, 永島玄, 堀池周, 花島隆泰, 黒川雄一郎, 湯浅裕美, 90度磁気結合膜のX線反射率による構造解析, 第66回応用物理学会春季学術講演会, 2019.03.
7.	黒川雄一郎，若江将和，鷲見聡，粟野博之，大西紘平，湯浅裕美, 希土類合金磁性細線を用いた電流誘起磁壁移動の温度依存性の測定, 電気学会マグネティックス／電子材料合同研究会, 2019.03.
8.	Yuichiro Kurokawa, Current-induced domain wall motion in rare-earth transition-metal alloy magnetic wire for future memory, CARN-OSAKA Annual Workshop 2018, 2018.12.
9.	Yuichiro Kurokawa, Satoshi Sumi, Hiroyuki Awano, Hiromi Yuasa, Multilayered current-induced domain wall motion for high density magnetic memory, 9th Joint European Magnetic Symposia, 2018.09.
10.	Masakazu Wakae, Yuichiro Kurokawa, Hiromi Yuasa, Observation of Spin-Orbit Torque Magnetization Switching in Gd-Fe Perpendicular Magnetized Wire without External Magnetic Field, 2018 International Conference on Solid State Devices and Materials, 2018.09.
11.	Masakazu Wakae, Yuichiro Kurokawa, Hiromi Yuasa, Observation of spin-orbit torque magnetization switching in Gd-Fe perpendicular magnetized wire without external magnetic field, 第65回応用物理学会春季学術講演会, 2018.03.
12.	Yuichiro Kurokawa, Masakazu Wakae, Ryogo Yoshimura, Hiroyasu Kondo, Satoshi Sumi, Hiroyuki Awano, Hiromi Yuasa, Investigation of current-induced domain wall motion in Gd-Fe wire with low domain wall propagation filed, 第65回応用物理学会春季学術講演会, 2018.03.
13.	Yuichiro Kurokawa, Current-induced domain wall motion in rare-earth transition-metal alloy magnetic wire, SKKU and Kyushu university Joint Workshop, 2018.01.

学会活動

所属学会名

日本磁気学会

応用物理学会

日本物理学会

学協会役員等への就任

2023.04～2026.03, 電気学会マグネティックス研究会, 委員.

2021.04～2025.03, 日本磁気学会, 企画委員.

学会大会・会議・シンポジウム等における役割

2022.09.16～2022.09.16, 第75回電気・情報関係学会九州支部連合大会, 座長.

2023.09.07～2023.09.07, 日本磁気学会第46回学術講演会, 座長.

2021.09.25～2021.09.26, 電気関係学会九州支部第74回連合大会, 座長.

2021.08.31～2021.09.02, 第45回　日本磁気学会学術講演会, 座長.

2020.06.03～2020.06.04, Spin-RNJ 若手オンライン研究発表会, 座長.

2018.12.08～2018.12.09, 平成30年度応用物理学会九州支部学術講演会, 座長.

2017.09.19～2017.09.22, 第41回日本磁気学会学術講演会, 会場係.

その他の研究活動

海外渡航状況, 海外での教育研究歴

massachusetts institute of technology, UnitedStatesofAmerica, 2019.04～2019.09.

Johannes Gutenberg-Universität Mainz, Germany, 2018.05～2018.09.

受賞

マグネティックス技術委員会研究奨励賞, 電気学会, 2019.03.

研究資金

科学研究費補助金の採択状況(文部科学省、日本学術振興会)

2022年度～2026年度, 国際共同研究強化(B), 分担, 情報キャリア磁気準粒子の制御に関する共同研究.

2021年度～2023年度, 基盤研究(C), 分担, 逆スピンホール効果による電流と三次元スピン偏極分布の同時測定.

2021年度～2022年度, 若手研究, 代表, 二成分スピントルク項に基づく希土類フェリ磁性薄膜中スピントルクの新解釈.

2018年度～2019年度, 若手研究, 代表, 電流-磁区経路分離型磁壁移動スピンロジックによる不揮発性論理回路の開発.

競争的資金(受託研究を含む)の採択状況

2022年度～2024年度, 日本-台湾研究交流「AIシステム構成に資するナノエレクトロニクス技術」, 分担, 水素化により制御されたスピンネットワークを利用した万能なニューロモルフィックシステム.

2021年度～2023年度, 戦略的創造研究推進事業 (文部科学省), 代表, 高度な柔軟性を有するIoTスピンデバイス開発.

寄附金の受入状況

2023年度, 村田学術振興財団, 研究助成/自由に設計可能なプリンタブル回路を用いた不揮発性フレキシブルレーストラックメモリ実装の試み.

2023年度, 荏原・畠山記念文化財団, 研究助成/大面積オールプリンテッドスピンゼーベック熱電変換デバイスの開発.

2021年度, パロマ環境技術開発財団, 研究助成金/無給電温度・ガスセンシングのための薄型スピンゼーベック熱発電素子の作製(継続).

2021年度, 服部報公会, 工学研究奨励援助金/多層磁気記録層を有する大容量3次元磁性細線メモリの開発.

2020年度, パロマ環境技術開発財団助成金, 無給電温度・ガスセンシングのための薄型スピンゼーベック熱発電素子の作製.

2018年度, マツダ財団, マツダ研究助成/ナノピラー型磁性細線を利用した大容量三次元磁壁移動型細線メモリの実現の試み.

2017年度, 池谷科学技術振興財団, 単年度研究助成/重金属サンドイッチ構造を利用した二重スピントルクによる磁壁移動の研究.

2017年度, 中部電気利用基礎研究振興財団, 研究助成/磁性細線メモリの熱アシストによる高性能化.

学内資金・基金等への採択状況

2017年度～2017年度, 平成２９年度エネルギー研究教育機構若手研究者・博士課程学生支援プログラム, 代表, 希土類アモルファス磁性体を用いたスピンゼーベック熱電変換の研究.

九大関連コンテンツ

pure2017年10月2日から、「九州大学研究者情報」を補完するデータベースとして、Elsevier社の「Pure」による研究業績の公開を開始しました。

QIR　九州大学学術情報リポジトリシステム情報科学研究院

システム情報科学研究院


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