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Microstructural changes in high-coercivity Zn-bonded Sm-Fe-N magnets

Journal of Magnetism and Magnetic Materials 510, 166943-1~8,

2020年4月1日(水)

M. Matsuura, K. Yamamoto, N. Tezuka, and S. Sugimoto

Abstract

In this study, the relationship between the microstructural and coercivity changes of Zn-bonded Sm-Fe-N magnets was investigated. A Zn-bonded Sm-Fe-N magnet prepared using a fine Zn powder with a low O content exhibited a high coercivity of 2.7 MA m−1, whereas a Zn-free magnet displayed a low coercivity of only 0.31 MA m−1. The raw commercial Sm-Fe-N powder contained an oxidized layer at the surface of the powder with a thickness of approximately 13 nm. In the Zn-free Sm-Fe-N magnet, O diffused into interior of Sm2Fe17N3 grains to generate coarse α-Fe grains with diameters of several tens of nanometers in the oxidized layer. In the high-coercivity Zn-bonded magnet, a Zn-rich region existed at the surface of the Sm2Fe17N3 grains. In the Zn-diffused region, Fe, Zn, Sm, and O were detected via transmission electron microscopy / energy-dispersive X-ray analysis, and this region contained fine grains of Γ-FeZn, α-FeZn, and Sm-O. The non-magnetic Γ-FeZn phase served to magnetically isolate the soft magnetic α-FeZn phase from the Sm2Fe17N3 phase, resulting in the Zn-bonded Sm-Fe-N magnet with high coercivity.


その他特記事項

This work was (in part) supported by the Elements Strategy Initiative Center for Magnetic Materials (ESICMM), Grant Number JPMXP0112101004, through the Ministry of Education, Culture, Sports, Science and Technology (MEXT).


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文部科学省
元素戦略プロジェクト(活動紹介)
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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