Magnetization reversal analysis of permanent magnet considering local demagnetizing field

• Project/Area Number: 17H03376
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Physical properties of metals/Metal-base materials
• Research Institution: Tohoku University
• Principal Investigator: Kitakami Osamu 東北大学, 多元物質科学研究所, 教授 (70250834)
• Co-Investigator(Kenkyū-buntansha): 岡本 聡 東北大学, 多元物質科学研究所, 准教授 (10292278) ; 菊池 伸明 東北大学, 多元物質科学研究所, 助教 (80436170)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥13,130,000 (Direct Cost: ¥10,100,000、Indirect Cost: ¥3,030,000); Fiscal Year 2019: ¥3,640,000 (Direct Cost: ¥2,800,000、Indirect Cost: ¥840,000); Fiscal Year 2018: ¥3,640,000 (Direct Cost: ¥2,800,000、Indirect Cost: ¥840,000); Fiscal Year 2017: ¥5,850,000 (Direct Cost: ¥4,500,000、Indirect Cost: ¥1,350,000)
• Keywords: 永久磁石 / 磁化反転 / 保磁力 / 磁壁 / 粒界 / 磁壁移動 / NdFeB / ナノコンポジット / 単一粒子 / 反転核生成 / NdFeB磁石 / 幾何形状 / 反磁場 / ＮｄＦｅＢ / 磁石 / 局所反磁場

Outline of Final Research Achievements

NdFeB magnets play crucial roles in modern technologies, such as electric vehicles and power generators. At high operation temperatures, however, the performance severely deteriorates due to the coercivity decay. The aim of the present study is to clarify how one can enhance the coercivity by revealing the magnetization process.
We have carefully traced elementary magnetization processes occurring in single nanostructured NdFeB magnets consisting of a few magnetic domains by means of the highly sensitive magnetization detection technique and the x-ray circular dichroism. It has been found that the magnetization proceeds by domain wall displacement and the coercivity is dominated by the pinning of the domain walls at crystal grain boundaries. According to the micromagnetics simulation as well as the experiment mentioned above, the coercivity is found to be effectively enhanced by weakening the exchange stiffness of the boundary phase.

Academic Significance and Societal Importance of the Research Achievements

低環境負荷の先端技術を支える材料としてNdFeB磁石は重要な役割を果たしている．それらのエネルギー利用効率向上には，一層の保磁力増強が切望されている．本研究では，各種先端技術を組み合わせることにより，NdFeB磁石内で起きる磁化反転の素過程を詳細に調べ，その保磁力が結晶粒界の磁壁ピニング力に支配されることを初めて明らかにした．保磁力に及ぼす粒界制御の影響については長年議論されてきたが，本研究はその重要性を初めて実証したものである．この成果に基づけば，粒界を非磁性化に向かわせる元素添加もしくは組織制御プロセスの最適化により，さらなる高保磁力化を実現できる可能性がある．

Research Products

• [Journal Article] Imaging of transient magnetization dynamics of Co/Pt multilayer dots with X-ray magnetic circular dichroism excited by microwaves (2020)
  • Author(s): Kikuchi N.、Yomogita T.、Sato K.、Okamoto S.、Kitakami O.、Osawa H.、Suzuki M.、Toyoki K.、Kotani Y.、Nakamura T.
  • Journal Title: Japanese Journal of Applied Physics Volume: 59 Issue: SE Pages: SEED03-SEED03
  • DOI: 10.35848/1347-4065/ab6cb1
  • Peer Reviewed / Open Access
• [Journal Article] Tunnel magnetocapacitance in Fe/MgF2 single nanogranular layered films (2020)
  • Author(s): Msiska Robin、Honjo Shusaku、Asai Yuki、Arita Masashi、Tsurumaki-Fukuchi Atsushi、Takahashi Yasuo、Hoshino Norihisa、Akutagawa Tomoyuki、Kitakami Osamu、Fujioka Masaya、Nishii Junji、Kaiju Hideo
  • Journal Title: Applied Physics Letters Volume: 116 Issue: 8 Pages: 082401-082401
  • DOI: 10.1063/1.5139702
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Temperature dependent magnetization reversal process of a Ga-doped Nd-Fe-B sintered magnet based on first-order reversal curve analysis (2019)
  • Author(s): Okamoto Satoshi、Miyazawa Kazunori、Yomogita Takahiro、Kikuchi Nobuaki、Kitakami Osamu、Toyoki Kentaro、Billington David、Kotani Yoshinori、Nakamura Tetsuya、Sasaki Taisuke、Ohkubo Tadakatsu、Hono Kazuhiro、Takada Yukio、Sato Takashi、Kaneko Yuji、Kato Akira
  • Journal Title: Acta Materialia Volume: 178 Pages: 90-98
  • DOI: 10.1016/j.actamat.2019.08.004
  • Peer Reviewed
• [Journal Article] Microwave-assisted switching in CoCrPt granular medium under continuous microwave fields (2019)
  • Author(s): Kikuchi Nobuaki、Sato Katsunari、Kikuchi Shun、Okamoto Satoshi、Shimatsu Takehito、Kitakami Osamu、Osawa Hitoshi、Suzuki Motohiro
  • Journal Title: Journal of Applied Physics Volume: 126 Issue: 8 Pages: 083908-083908
  • DOI: 10.1063/1.5111576
  • Peer Reviewed / Open Access
• [Journal Article] Detection of elemental magnetization reversal events in a micro-patterned Nd-Fe-B hot-deformed magnet (2019)
  • Author(s): Yomogita Takahiro、Kikuchi Nobuaki、Okamoto Satoshi、Kitakami Osamu、Sepehri-Amin Hossein、Ohkubo Tadakatsu、Hono Kazuhiro、Hioki Keiko、Hattori Atsushi
  • Journal Title: AIP Advances Volume: 9 Issue: 12
  • DOI: 10.1063/1.5129830
  • Peer Reviewed / Open Access
• [Journal Article] First-order reversal curve analysis of a Nd-Fe-B sintered magnet with soft X-ray magnetic circular dichroism microscopy (2019)
  • Author(s): Miyazawa Kazunori、Okamoto Satoshi、Yomogita Takahiro、Kikuchi Nobuaki、Kitakami Osamu、Toyoki Kentaro、Billington David、Kotani Yoshinori、Nakamura Tetsuya、Sasaki Taisuke、Ohkubo Tadakatsu、Hono Kazuhiro
  • Journal Title: Acta Materialia Volume: 162 Pages: 1-9
  • DOI: 10.1016/j.actamat.2018.09.053
  • Peer Reviewed
• [Journal Article] Confirmation of Hard Magnetic L10 FeNi Phase Precipitated in FeNiSiBPCu Alloy by Anomalous X-Ray Diffraction (2018)
  • Author(s): Sharma Parmanand、Okamoto Satoshi、Tajiri Hiroo、Sato Kazuhisa、Zhang Yan、Kitakami Osamu、Makino Akihiro
  • Journal Title: IEEE Transactions on Magnetics Volume: 54 Issue: 11 Pages: 1-5
  • DOI: 10.1109/tmag.2018.2842057
  • Peer Reviewed
• [Journal Article] Robustness of Voltage-induced Magnetocapacitance (2018)
  • Author(s): H. Kaiju, T. Misawa, T. Nagahama, T. Komine, O. Kitakami, M. Fujioka, J. Nishii, and G. Xiao
  • Journal Title: Scientific Reports Volume: 8 Issue: 1
  • DOI: 10.1038/s41598-018-33065-y
  • NAID: 120006536950
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Temperature and field direction dependences of first-order reversal curve (FORC) diagrams of hot-deformed Nd-Fe-B magnets (2018)
  • Author(s): Yomogita Takahiro、Okamoto Satoshi、Kikuchi Nobuaki、Kitakami Osamu、Sepehri-Amin Hossein、Ohkubo Tadakatsu、Hono Kazuhiro、Akiya Takahiro、Hioki Keiko、Hattori Atsushi
  • Journal Title: Journal of Magnetism and Magnetic Materials Volume: 447 Pages: 110-115
  • DOI: 10.1016/j.jmmm.2017.09.072
  • Peer Reviewed
• [Journal Article] Time and Spatially Resolved Hard X-Ray MCD Measurement on a Co/Pt Multilayer Dot Excited by Pulsed RF Field (2018)
  • Author(s): Nobuaki Kikuchi, Hitoshi Osawa, Motohiro Suzuki, and Osamu Kitakami
  • Journal Title: IEEE Transactions on Magnetics Volume: 54 Issue: 2 Pages: 1-6
  • DOI: 10.1109/tmag.2017.2745211
  • Peer Reviewed
• [Journal Article] Novel torque magnetometry for uniaxial anisotropy constants of thin films and its application to FePt granular thin films (2018)
  • Author(s): Takuya Ono, Nobuaki Kikuchi, Satoshi Okamoto, Osamu Kitakami, and Takehito Shimatsu
  • Journal Title: Applied Physics Express Volume: 11 Issue: 3 Pages: 033002-033002
  • DOI: 10.7567/apex.11.033002
  • NAID: 210000136131
  • Peer Reviewed
• [Journal Article] Magnetic characteristics and nanostructures of FePt granular flms with GeO2 segregant (2017)
  • Author(s): T. Ono, T. Moriya, M. Hatayama, K. Tsumura, N. Kikuchi, S. Okamoto, O. Kitakami, T. Shimatsu
  • Journal Title: Applied Physics Letters Volume: 110 Issue: 2
  • DOI: 10.1063/1.4973473
  • Peer Reviewed
• [Journal Article] Significant modification of perpendicular magnetic anisotropy of W/Fe(001) multilayer (2017)
  • Author(s): Y. Matsumoto, Y. Miura, S. Okamoto, N. Kikuchi, O. Kitakami
  • Journal Title: Applied Physics Express Volume: 10 Issue: 6 Pages: 063005-063005
  • DOI: 10.7567/apex.10.063005
  • Peer Reviewed
• [Journal Article] Magnetization Reversal of Nd-Fe-B Thin Film under a Nano-second Pulse Magnetic Field (2017)
  • Author(s): 門ノ沢 和也, 菊池 伸明, 後藤 龍太, 岡本 聡, 北上 修
  • Journal Title: IEEJ Transactions on Fundamentals and Materials Volume: 137 Issue: 7 Pages: 374-379
  • DOI: 10.1541/ieejfms.137.374
  • NAID: 130006839843
  • ISSN: 0385-4205, 1347-5533
  • Peer Reviewed
• [Journal Article] First-order Reversal Curve (FORC) Analysis and Its Application for Permanent Magnet Materials (2017)
  • Author(s): 岡本 聡, 蓬田貴裕, 宮澤和則, 菊池伸明, 北上 修, 渡辺奈生巳, 吹田尚久
  • Journal Title: Materia Japan Volume: 56 Issue: 9 Pages: 533-540
  • DOI: 10.2320/materia.56.533
  • NAID: 130006038186
  • ISSN: 1340-2625, 1884-5843
  • Peer Reviewed
• [Presentation] W下地を用いたSm(Fe,Ti)12エピタキシャル微粒薄膜の作製 (2019)
  • Author(s): 近藤 司, 岡本 聡, 菊池伸明, 芳賀僚太, 北上 修
  • Organizer: 電気学会マグネティクス研究会
• [Presentation] CoCrPtグラニュラー薄膜における磁性粒子間交換結合のマイクロ波アシスト磁化反転への影響 (2019)
  • Author(s): 佐藤勝成, 菊池伸明, 岡本 聡, 北上 修, 島津武仁
  • Organizer: 電気学会マグネティクス研究会
• [Presentation] Detection of elemental magnetization reversal events in a micropatterned hot-deformed Nd-Fe-B magnet (2019)
  • Author(s): T. Yomogita, N. Kikuchi, S. Okamoto, O.Kitakami, H. Sepehri-Amin, T. Ohkubo, K. Hono, K. Hioki, A. Hattori
  • Organizer: 64th Annual Conference on Magnetism and Magnetic Materials
  • Int'l Joint Research
• [Presentation] Temperature dependent magnetization reversal process of a Ga-doped Nd-Fe-B sintered magnet based on first-order reversal curve analysis (2019)
  • Author(s): Satoshi Okamoto, Kazunori Miyazawa, Takahiro Yomogita, Nobuaki Kikuchi, Osamu Kitakami, Kentaro Toyoki, David Billington, Yoshinori Kotani, Tetsuya Nakamura, Taisuke Sasaki, Tadakatsu Ohkubo, Kazuhiro Hono, Yukio Takada, Takashi Sato, Yuji Kaneko, Akira Kato
  • Organizer: 64th Annual Conference on Magnetism and Magnetic Materials
  • Int'l Joint Research
• [Presentation] Transient magnetization dynamics of a Co/Pt multilayer dot probed by XMCD (2019)
  • Author(s): N. Kikuchi, T. Yomogita, K. Sato, S. Okamoto, O. Kitakami, H. Osawa, M. Suzuki, K. Toyoki, Y. Kotani and T. Nakamura
  • Organizer: The 19th International Conference on Solid Films and Surfaces
  • Int'l Joint Research / Invited
• [Presentation] Sm(Fe,Ti)12エピタキシャル微粒子薄膜の作製 (2019)
  • Author(s): 近藤司, 岡本聡, 菊池伸明, 北上修
  • Organizer: 第43回日本磁気学会学術講演会
• [Presentation] 軟 X 線 MCD 顕微分光による熱間加工磁石の磁化過程評価 (2019)
  • Author(s): 竹内誠, 蓬田貴裕, 菊池伸明, 岡本聡, 北上修, 豊木研太郎, 小林慎太郎, 小谷佳範, 中村哲也, 服部篤, 日置敬子
  • Organizer: 第43回日本磁気学会学術講演会
• [Presentation] 微細加工した熱間加工Nd-Fe-B磁石の磁化反転素過程計測 (2019)
  • Author(s): 蓬田貴裕, 菊池伸明, 岡本聡, 北上修, H. Sepehri-Amin, 大久保忠勝, 宝野和博, 日置敬子, 服部篤
  • Organizer: 第43回日本磁気学会学術講演会
• [Presentation] Nd-Fe-B 焼結磁石の FORC 解析 (2019)
  • Author(s): 宮澤 和則, 岡本 聡, 蓬田 貴裕, 菊池 伸明, 北上 修
  • Organizer: 電気学会A部門大会
• [Presentation] 軟X線MCD顕微分光による熱間加工磁石の磁化過程観察 (2019)
  • Author(s): 竹内誠, 蓬田貴裕, 菊池伸明, 岡本聡, 北上修, 豊木研太郎, 小林慎太郎, 小谷佳範, 中村哲也, 服部篤, 日置敬子
  • Organizer: 電気学会マグネティクス研究会
• [Presentation] 熱間加工Nd-Fe-B磁石の微小領域の高感度磁化測定 (2018)
  • Author(s): 蓬田貴裕, 岡本聡, 菊池伸明, 北上修, Hossein Sepehri Amin, 大久保忠勝, 宝野和博, 秋屋貴博, 日置 敬子, 服部篤
  • Organizer: 日本金属学会
• [Presentation] Microwave-assisted switching behavior of CoCrPt based granular media (2018)
  • Author(s): N. Kikuchi, K. Shimada, S. Kikuchi, K. Sato, S. Okamoto, O. Kitakami, T. Shimatsu
  • Organizer: The 29th The Magnetic Recording Conference (TMRC 2018)
  • Int'l Joint Research / Invited
• [Presentation] Confirmation of Hard Magnetic L10 FeNi phase precipitated in FeNiSiBPCu alloy by Anomalous X-ray Diffraction (2018)
  • Author(s): P. Sharma, S. Okamoto, H. Tajiri, K. Sato, Y. Zhang, O. Kitakami, A. Makino
  • Organizer: INTERMAG 2018
  • Int'l Joint Research
• [Presentation] 熱間加工Nd-Fe-B磁石の微小領域の高感度磁化測定 (2018)
  • Author(s): 蓬田貴裕, 岡本聡, 菊池伸明, 北上修, Hossein Sepehri Amin, 大久保忠勝, 宝野和博, 秋屋貴博, 日置 敬子, 服部篤
  • Organizer: 日本磁気学会学術講演会
• [Presentation] ナノXMCD顕微鏡によるNd-Fe-B商用焼結磁石のFORC解析 (2018)
  • Author(s): 宮澤和則, 蓬田貴裕, 岡本聡, 菊池伸明, 北上修, 豊木研太郎, David Billington, 小谷佳範, 中村哲也, 佐々木泰祐, 大久保忠勝, 宝野和博
  • Organizer: 日本金属学会
• [Presentation] ナノXMCD顕微鏡によるNd-Fe-B商用焼結磁石のFORC解析 (2018)
  • Author(s): 宮澤和則, 蓬田貴裕, 岡本聡, 菊池伸明, 北上修, 豊木研太郎, David Billington, 小谷佳範, 中村哲也, 佐々木泰祐, 大久保忠勝, 宝野和博
  • Organizer: 日本金属学会春季講演会
• [Presentation] 熱間加工Nd-Fe-B磁石の 微小領域の高感度磁化測定 (2018)
  • Author(s): 蓬田貴裕, 岡本聡, 菊池伸明, 北上修, H. Sepehri-Amin, 大久保忠勝, 宝野和博, 秋屋貴博, 日置敬子, 服部篤
  • Organizer: 日本金属学会春季講演会
• [Presentation] Elementally-resolved ferromagnetic resonance by X-ray magnetic circular dichroism on Co/Pt multilayer dots (2018)
  • Author(s): N. Kikuchi, Y. Yomogita, D. Kanahara, S. Okamoto, O. Kitakami, T. Shimatsu, Y. Kotani, K. Toyoki, H. Osawa5, M. Suzuki, T. Nakamura
  • Organizer: Magnetics and Optics Research International Symposium (MORIS2018)
  • Int'l Joint Research
• [Presentation] 時間分解XMCDによる磁化ダイナミクス計測 (2017)
  • Author(s): 菊池伸明
  • Organizer: 用スピントロニクス新分野創成研究会
  • Invited
• [Presentation] 時間・空間分解XMCDによる強磁性共鳴測定 (2017)
  • Author(s): 菊池伸明
  • Organizer: 日本物理学会
  • Invited
• [Presentation] 熱間加工Nd-Fe-B磁石の表面加工ダメージの影響 -微小磁石の磁化過程解析に向けて- (2017)
  • Author(s): 蓬田貴裕, 岡本 聡, 菊池伸明, 北上 修, H. Sepehri-Amin, Lihua Liu, 大久保忠勝, 宝野和博, 秋屋貴博, 日置敬子, 服部篤
  • Organizer: 日本金属学会
• [Presentation] Ga添加焼結Nd-Fe-B磁石のFORC解析 (2017)
  • Author(s): 宮澤和則, 蓬田貴裕, 岡本聡, 菊池伸明, 北上修, 佐々木泰祐, 大久保忠勝, 宝野和博, 高田幸生, 佐藤岳, 金子裕治, 加藤晃
  • Organizer: 日本磁気学会
• [Presentation] Analyses on Magnetization Reversal Process of Nd-Fe-B Hot-Deformed Magnets (2017)
  • Author(s): S. Okamoto, T. Yomogita, L. Zhang, N. Kikuchi, O. Kitakami, H. Sepehri-Amin, T. Ohkubo, K. Hono, T. Akiya, K. Hioki, A. Hattori
  • Organizer: TMS 2017 Annual Meeting & Exhibition
  • Int'l Joint Research / Invited
• [Presentation] Coercivity mechanism of Nd-Fe-B magnets based on magnetic viscosity and FORC measurements (2017)
  • Author(s): S. Okamoto, T. Yomogita, L. Zhang, N. Kikuchi, O. Kitakami, H. Sepehri-Amin, T. Ohkubo, K. Hono, T. Akiya, K. Hioki, A. Hattori
  • Organizer: 3N-Lab Workshop on Permanent Magnets
  • Int'l Joint Research / Invited
• [Presentation] Time and spatial resolved XMCD-FMR measurement on a Co/Pt multilayer dot excited by rf magnetic field in GHz regime (2017)
  • Author(s): Nobuaki Kikuchi, Hitoshi Osawa, Motohiro Suzuki, Osamu Kitakami
  • Organizer: IEEE Magnetic Recording Conference
  • Int'l Joint Research / Invited
• [Presentation] First-order reversal curve analysis of hot-deformed Nd-Fe-B magnets (2017)
  • Author(s): K. Miyazawa,T. Yomogita, S. Okamoto, N. Kikuchi, O. Kitakami,T. Akiya, K. Hioki, A. Hattori
  • Organizer: International Workshop on Nanostructured Magnetic Materials
  • Int'l Joint Research
• [Presentation] Time- and spatially resolved hard X-ray MCD with pulsed rf field excitation on a Co/Pt multilayer dot (2017)
  • Author(s): N. Kikuchi, T. Yomogita, D. Kanahara, S. Okamoto, O. Kitakami, T. Shimatsu, H. Osawa, M. Suzuki
  • Organizer: ＭＭＭ2017
  • Int'l Joint Research