Magnetism of ultrathin intergranular boundary regions in Nd-Fe-B permanent magnets

Yasukazu Murakami, T. Tanigaki, T. T. Sasaki, Y. Takeno, H. S. Park, T. Matsuda, T. Ohkubo, K. Hono, D. Shindo

Research output: Contribution to journalArticlepeer-review

69 Citations (Scopus)

Abstract

The magnetism of a thin grain-boundary (GB) phase that envelopes the Nd2Fe14B grains in optimally annealed Nd-Fe-B sintered magnets was investigated by electron holography. The phase shift measured from a thin-foil specimen containing a tilted amorphous GB phase (∼3 nm in width) was -0.34 rad, which is substantially smaller than that expected for the nonferromagnetic GB phase of -1.2 rad. Simulations of the phase shift with various magnetization values suggest that the magnetic flux density of the GB phase is ∼1.0 T. The observations imply significant exchange coupling between Nd2Fe14B grains, which can explain the avalanche propagation of magnetization reversal observed in sintered magnets.

Original languageEnglish
Pages (from-to)370-379
Number of pages10
JournalActa Materialia
Volume71
DOIs
Publication statusPublished - 2014 Jun

Keywords

  • Coercivity
  • Grain boundary
  • Nanostructure
  • Permanent magnets
  • Transmission electron microscopy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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