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Ab-initio simulation of Ga-doped Nd-Fe-B magnets

IcAUMS 2018(済州島, 韓国)

2018年6月7日(木)

Yasutomi Tatetsu and Yoshihiro Gohda

Abstract

Nd-Fe-B sintered magnets are used in various kinds of application, mainly in motors because of having the largest (BH)max among permanent magnets. In general, understanding of grain boundaries in materials is very important from the aspect of controlling those of physical properties and this can be also applicable to Nd-Fe-B magnets. The magnetic instability of Nd-Fe-B magnets, especially the coercivity, at high temperatures is a critical issue for keeping a good performance of Nd-Fe-B magnets, however, the mechanism is still unclear. Several experimental studies have been clarifying important relationships between the coercivity and the grain boundaries which are constructed by Nd2Fe14B main grains and subphases. As reported in several experimental studies for Nd-Fe-B magnets, adding Ga into Nd-Fe-B magnets increases the coercivity of Nd-Fe-B magnets. Nd6Fe13Ga exists around the triple junctions of coercivity-improved Nd-Fe-B magnets. We calculated the magnetic anisotropy K1 of Nd in Nd2Fe14B/Nd6Fe13Ga grain-boundary (GB) model from first principles to understand the relationship between the coercivity improvement and the Nd6Fe13Ga existence around the interface of Nd-Fe-B magnets. We used the computational code OpenMX. From the analysis of the magnetic anisotropy K1 of Nd at the interface, we find that K1 of GB model systems is much higher than K1 of Nd which is exposed to vacuum at a surface. Especially K1 of the several GB model systems is comparable to that of the Nd2Fe14B bulk. This K1 improvement suggests the importance of the Nd6Fe13Ga existence around the interface of Nd-Fe-B magnets to obtain higher coercivity.


研究活動

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