永久磁石材料における保磁力解析と磁化反転機構

During the last decade, coercivity enhancement of permanent magnets has been one of the major issues due to the strong demands of high-performance magnets for the traction motors of electric/hybrid vehicles. For this purpose, the study on the coercivity mechanism of permanent magnets is essentially important. However, this has been uncleared regardless of the past long-discussed studies. Recently, we have tacked this issue using the multi-scale coercivity analysis. As macroscopic coercivity analyses, two different approaches were employed. One was the first-order reversal curve (FORC) analysis, which revealed the dominant magnetization reversal process, i.e., single- or multi-domain magnetization reversal. The other was the energy barrier analysis based on the magnetic viscosity measurements. On the other hand, as a microscopic coercivity analysis, an elemental-magnetization reversal measurement was attempted. In this paper, these multi-scale coercivity analyses have been reviewed.