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Effect of the surface magnetic anisotropy of neodymium atoms on the coercivity in neodymium permanent magnets

Phys. Rev.B 103, 014418

2021年1月13日(水)

Masamichi Nishino, Ismail Enes Uysal, and Seiji Miyashita

Abstract

The Nd permanent magnet (Nd2Fe14B) is an indispensable material used in modern energy conversion devices. The realization of high coercivity at finite temperatures is an important issue. One of the important ingredients for controlling the coercive force is the surface property of magnetic grains. It has been found by first-principles studies that the Nd atoms in the first (001) surface layer facing the vacuum have in-plane anisotropy perpendicular to the caxis, which may decrease the coercivity. Focusing on the surface anisotropy effect on the coercivity, we examine the coercivity at zero and finite temperatures using an atomistic model reflecting the lattice structure of the Nd magnet with a stochastic Landau-Lifshitz-Gilbert equation method. We study three general cases, in which the Nd atoms in surface layers have (1) no anisotropy, (2) in-plane anisotropy, and (3) reinforced anisotropy for two types of surface, (001) and (100) surfaces. We find that in contrast to the zero-temperature case, owing to the thermal fluctuation effect, the modification of only the first surface layer has little effect on the coercivity at finite temperatures. However, the modification of a few layers results in significant effects. We discuss the details of the dependences of the coercivity on temperature, the type of surface, and modified layer depth, and also the features of domain growth in magnetization reversal.




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