Abstract
Effective grain interface modification was conducted to increase the coercivity of Nd–Fe–B sintered magnets without degrading their magnetic properties seriously. The surface of magnet pieces (3.0×3.0×2.8 mm3) was uniformly coated with a Dy or Tb metal film, and then each metal was introduced inside the magnets through the Nd-rich grain boundary regions for enriching them on the surface around the Nd2Fe14B grain particles. The coercivities of the Dy- and Tb-metal-treated magnets (HcJ = 1.45 and 1.81 MA/m, respectively) were considerably improved compared with that of the untreated magnet (HcJ = 0.98 MA/m), suggesting that the aligned magnetic domain structure was effectively stabilized by such a Dy- or Tb-enriched interface around the Nd2Fe14B grain particles.