Estimation of demagnetization curve of magnet with nonuniform coercivity

Takayuki Tokushige, Masafumi Umabuchi, Daisuke Miyagi, Norio Takahashi, Masaru Ito, Koichi Hirota

Research output: Contribution to journalArticlepeer-review


Neodymium-iron-boron (Nd-Fe-B) magnets exhibit exceedingly high maximum energy products and remanences. Their coercivities, however, decrease rapidly with increasing the temperature, and the magnets are easily demagnetized at elevated temperatures. To reduce the effects of temperature, the coercivity at the room temperature is enhanced by the addition of the dysprosium (Dy), which causes a reduction in remanence. The Grain Boundary Diffusion process is a technology to enhance coercivities while suppressing a large reduction in remanences. Dy that is effective for the coercivity enhancement is supplied from the magnet surface and diffused into the magnets through the grain boundary phase, and then put at the grain surface. When the Grain Boundary Diffusion process is applied to relatively large magnets, the partial coercivities near the magnet surface, where higher coercivities are generally required, can be enhanced effectively. In other words, the magnets exhibit nonuniform coercivity. We have conceived a simple and effective method for estimating the demagnetization curves of such nonuniform coercivity magnets. In this paper, the validity of the estimation method was examined.

Original languageEnglish
Pages (from-to)101-107
Number of pages7
JournalIEEJ Transactions on Fundamentals and Materials
Issue number1
Publication statusPublished - 2012 Feb 13


  • Coercivity distribution magnet
  • Estimation of demagnetization curve

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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