RFeB-BASED MAGNET AND PROCESS FOR PRODUCING RFeB-BASED MAGNET

摘要

The purpose of the present invention is to provide an RFeB system sintered magnet which has a high and uniform level of coercivity over the entirety of the single magnet even if the magnet is comparatively thick. The present invention is an RFeB system sintered magnet in which a heavy rare-earth element R H which is at least one kind of rare-earth element selected from the group of Dy, Tb and Ho is diffused into a base material through the grain boundaries of the same base material made of a sintered compact of an RFeB system magnet containing R L , Fe and B, where R L represents a light rare-earth element which is at least one kind of rare-earth element selected from the group of Nd and Pr, wherein: the size of the RFeB system sintered magnet at a smallest-size portion is greater than 3 mm; the amount of heavy rare-earth element R H contained in the RFeB system sintered magnet divided by the volume of the RFeB system sintered magnet is equal to or greater than 25 mg/cm 3 ; and the difference between a local coercivity at the surface of the smallest-size portion and a local coercivity in the central region of the smallest-size portion is equal to or less than 15 % of the local coercivity at the surface.