Role of atomic-scale thermal fluctuations in the coercivity

Yuta Toga, Seiji Miyashita, Akimasa Sakuma, Takashi Miyake

研究成果: Article査読

19 被引用数 (Scopus)


The microscopic mechanism of coercivity at finite temperature is a crucial issue for permanent magnets. Here we present the temperature dependence of the coercivity of an atomistic spin model for the highest-performance magnet Nd2Fe14B. For quantitative analysis of the magnetization reversal with thermal fluctuations, we focus on the free energy landscape as a function of the magnetization. The free energy is calculated by the replica-exchange Wang–Landau method. This approach allows us to address a slow nucleation problem, i.e., thermal activation effects, in the magnetization reversal. We concretely observed that the thermal fluctuations lead to a downward convexity in the coercivity concerning the temperature. Additionally, through analyzing the microscopic process of the thermal activation (nucleation), we discover the activation volume is insensitive to a magnetic field around the coercivity. The insensitivity explains the linear reduction of the free energy barrier by the magnetic field in the nucleation process.

ジャーナルnpj Computational Materials
出版ステータスPublished - 2020 12月 1

ASJC Scopus subject areas

  • モデリングとシミュレーション
  • 材料科学(全般)
  • 材料力学
  • コンピュータ サイエンスの応用


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