Computer Simulation of Enhancement of Coerciviy in Nd-Fe-B/(Nd,Dy)-Fe-B Composite Magnets

The coercivity Hc of Nd2Fe14B magnets and Nd2Fe14B/(Nd0.7Dy0.3)2Fe14B composite magnets were calculated by computer simulation based on the micromagnetic theory under assumptions that Nd2Fe14B and (Nd0.7Dy0.3)2Fe14B grains have magnetically deteriorated layers on their surfaces and diffusion of Dy from (Nd0.7Dy0.3)2Fe14B grains to Nd2Fe14B ones through the contacting boundaries recovers the magnetic anisotropy of the deteriorated layers of Nd2Fe14B grains. Hc of Nd2Fe14B/(Nd0.7Dy0.3)2Fe14B composite magnets increased by the diffusion of Dy from (Nd0.7Dy0.3)2Fe14B grains to Nd2Fe14B ones and the resultant recovery of the anisotropy field of deteriorated layers of Nd2Fe14B grains. The Hc vs fraction of (Nd0.7Dy0.3)2Fe14B grains curve were convex for the magnets with the degree of alignment between 0.94 and 0.99, which suggests that the above composite magnets have larger Hc values than the alloy-magnets with the same Dy content, and that we can save the consumption of Dy by using these composite magnets