ホーム > 研究活動 > 2018年 > First-order reversal curve analysis of a Nd-Fe-B sintered magnet with soft X-ray magneticcircular dichroism microscopy

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First-order reversal curve analysis of a Nd-Fe-B sintered magnet with soft X-ray magneticcircular dichroism microscopy

Acta Materialia Volume 162

2018年9月26日(水)

Kazunori Miyazawa, Satoshi Okamoto, Takahiro Yomogita, Nobuaki Kikuchi,Osamu Kitakami,Kentaro Toyoki, David Billington, Yoshinori Kotani,Tetsuya Nakamura, Taisuke Sasaki,Tadakatsu Ohkubo, Kazuhiro Hono ( https://doi.org/10.1016/j.actamat.2018.09.053 )

Abstract

First-order reversal curve (FORC) diagram, which visualizes the variation of magneticsusceptibility on a field plane, has been applied to a Nd-Fe-B sintered magnet. The FORCdiagram exhibits the characteristic behavior of two remarkable spots in low-field and high-fieldregions. The high-field FORC spot corresponds to the irreversible magnetization reversal at acoercive field, whereas the low-field FORC spot indicates the appearance of a large magneticsusceptibility state during the demagnetization process. Moreover, this low-field FORC spotbecomes dominant at high temperature, accompanied by a significant reduction in coercivity.These results suggest that the low-field FORC spot has a strong correlation with thedegradation of magnetic properties of a Nd-Fe-B sintered magnet. To clarify the actualmagnetization reversal processes corresponding to these two FORC spots, soft X-raymagnetic circular dichroism (XMCD) microscopy observation was employed with similar fieldsequences of the FORC measurements. Consequently, the low-field FORC spot is mainlyattributed to the domain wall motion in multi-domain grains, whereas the high-field FORC spotcorresponds to the magnetization reversal of single-domain grains. These indicate that aFORC diagram is a powerful evaluation method for the magnetization reversal processes ofpermanent magnets.

その他特記事項

We gratefully thank Dr. S. Hirosawa for valuable advice and fruitful discussion. This work was partially supported by Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials from MEXT, the Management Expenses Grants for National Universities Corporations from MEXT, JSPS KAKENHI Grant No. 17H03376, JST, Collaborative Research Based on Industrial Demand, and NIMS Joint Research Hub Program. The XMCD microscopy experiments have been performed at SPring-8 with the approval of JASRI (Proposal Nos. 2015A2042, 2015B1998, 2017A1022, and 2017B1028).


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文部科学省

文部科学省
元素戦略プロジェクト(活動紹介)
NIMS磁石パートナーシップ

元素戦略拠点

触媒・電池元素戦略拠点
触媒・電池元素戦略研究拠点 (京都大学)
東工大元素戦略拠点
東工大元素戦略拠点 (東京工業大学)
構造材料元素戦略研究拠点
構造材料元素戦略研究拠点 (京都大学)
高効率モーター用磁性材料技術研究組合
高効率モーター用 磁性材料技術研究組合