Effect of Dy-diffusion Treatment on Coercivity and Magnetic Domain Structure of Nd-Fe-B Sintered Magnets

Abstract

Effects of Dy-diffusion treatment to Nd-Fe-B sintered magnets on those microstructure and coercivity were investigated. Coercivity of magnets increases in proportion with raising temperature of Dy-diffusion treatment and keeping longer term. As a result, it is found that changes of coercivity by this treatment can be classified into 2 modes: 1^st step shows a rapid increase in coercivity where Dy diffuses into grain boundary and surrounds grains. 2^nd step is a gradual increase in coercivity where Dy diffuses into 2-14-1 phases. As an extending study, we have tried to observe the magnetic domains of Nd-Fe-B sintered magnets by using XMCD-PEEM technique. It is found that Dy diffusion treatment suppresses the generation and the growth of magnetic reversed domains as same as Dy-doping into Nd-Fe-B magnets.