Anisotropy of rare-earth magnets

R. Skomski, D. J. Sellmyer

Research output: Contribution to journalArticle

49 Scopus citations

Abstract

Rare-earth intermetallics such as Nd2Fe14B and Sm-Co are widely used as high-performance permanent magnets, because they combine high magnetocrystalline anisotropy with reasonable magnetization and Curie temperature. The anisotropy is a combined effect of spin-orbit coupling and electrostatic crystal-field interactions. The main contribution comes from the rare-earth 4f electrons, which are well-screened from the crystalline environment but exhibit a strong spin-orbit coupling. In this limit, the magnetocrystalline anisotropy has a very transparent physical interpretation, the anisotropy energy essentially being equal to the energy of Hund's-rules 4f ion in the crystal field. The corresponding expression for the lowest-order uniaxial anisotropy constant K1 is used to discuss rare-earth substitutions, which have recently attracted renewed interest due to shifts in the rare-earth production and demand. Specific phenomena reviewed in this article are the enhancement of the anisotropy of Sm2Fe17 due to interstitial nitrogen, the use of Sm-Co magnets for high-temperature applications, and the comparison of rare-earth single-ion anisotropy with other single-ion and two-ion mechanisms.

Original languageEnglish (US)
Pages (from-to)675-679
Number of pages5
JournalJournal of Rare Earths
Volume27
Issue number4
DOIs
StatePublished - Aug 2009

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Keywords

  • crystal-field interaction
  • interstitial modification
  • magnetic anisotropy
  • permanent magnets
  • rare earths
  • spin-orbit coupling

ASJC Scopus subject areas

  • Chemistry(all)
  • Geochemistry and Petrology

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