High-magnetic-field annealing and coercivity in Sintered Nd-Fe-B Magnets

Hiroaki Kato, Takahiro Akiya, Kohki Takahashi

Research output: Contribution to journalReview articlepeer-review


Results of a systematic study concerned with the high-magnetic-field effects on the coercivity in processing various series of sintered Nd-Fe-B magnets are given. Coercivity enhancement phenomenon was observed in several series of sintered Nd-Fe-B magnets with Cu additive after annealing under magnetic fields of 10~14 T. A strong correlation was suggested between the field annealing temperature at which maximum coercivity increase was observed and the anomaly temperature in differential scanning calorimetry experiments. We found a linear relation between the room temperature coercivity H c of the sample annealed at T a=500°C under magnetic field H a for a series of samples with different Dy contents, which can be expressed as H c = H c(0) + αH a, with H c(0) being the value for the zero-field-annealed sample and α, the coercivity enhancement factor. Although very small, α has a positive finite value in samples with 0 mass% and 2 mass% Dy. Significant increase in α value was confirmed for samples with Dy content larger than 6 mass%\ This suggests the effects of higher anisotropy in paramagnetic susceptibility of Nd-rich intergranular phase containing Dy. Also introduced is the preliminary results of the grain boundary diffusion process of sinterd Nd- Fe-B samples with surface Dy layer under strong gradient magnetic fields produced by the 18 T superconducting magnets.

Original languageEnglish
Pages (from-to)72-80
Number of pages9
JournalNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
Issue number1
Publication statusPublished - 2012 Jan


  • Coercivity
  • High-magnetic-field processing
  • Sintered neodymium-iron-boron magnet

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry


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