First-principles calculations of magnetic properties for analysis of magnetization processes in rare-earth permanent magnets

Hiroki Tsuchiura, Takuya Yoshioka, Pavel Novák, Johann Fischbacher, Alexander Kovacs, Thomas Schrefl

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

It has been empirically known that the coercivity of rare-earth permanent magnets depends on the size and shape of fine particles of the main phase in the system. Also, recent experimental observations have suggested that the atomic-scale structures around the grain-boundaries of the fine particles play a crucial role to determine their switching fields. In this article, we review a theoretical attempt to describe the finite temperature magnetic properties and to evaluate the reduction of the switching fields of fine particles of several rare-earth permanent magnetic materials based on an atomistic spin model that is constructed using first-principles calculations. It is shown that, over a wide temperature range, the spin model gives a good description of the magnetization curves of rare-earth intermetallic compounds such as R 2Fe14B (R= Dy, Ho, Pr, Nd, Sm) and SmFe12. The atomistic spin model approach is also used to describe the local magnetic anisotropy around the surfaces of the fine particles, and predicts that the rare-earth ions may exhibit planar magnetic anisotropy when they are on the crystalline-structure surfaces of the particles. The dynamical simulation of the atomistic spin model and the corresponding micromagnetic simulation show that the planar surface magnetic anisotropy causes a reduction in the switching field of fine particles by approximately 20–30%, which may be relevant to the atomic-scale surface effects found in the experimental studies.

Original languageEnglish
Pages (from-to)748-757
Number of pages10
JournalScience and Technology of Advanced Materials
Volume22
Issue number1
DOIs
Publication statusPublished - 2021

Keywords

  • 106 Metallic materials; 401 1st principles methods
  • 40 Optical, magnetic and electronic device materials
  • 404 Dynamics simulations
  • 406 Multi-scale / multi-physics modelling
  • atomistic spin model
  • crystal field theory
  • first-principles calculations
  • micromagnetic simulations
  • Rare-earth permanent magnets

ASJC Scopus subject areas

  • Materials Science(all)

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