Patent ID: 6527822
Filing Date: 2003-03-04
Classification: B22F,B82Y,H01F

Abstract:
A rare earth-based permanent magnet which is a sintered body of a powder of a thin ribbon of a rare earth-based magnet alloy, having a metallographic phase structure of which the volume fraction of a four-phase region consisting of (a) an &agr;-iron phase having &agr;-iron grains with a grain diameter of 0.1 to 20 &mgr;m, (b) an R-rich phase which is a phase richer in the content of rare earth element than in an R2T14B phase, R being a rare earth element selected from praseodymium, neodymium, terbium and dysprosium, said R-rich phase having R-rich grains with a grain diameter of 0.1 to 20 &mgr;m, (c) an RxT4B4 phase, in which R has the same meaning as defined above, T is iron or a combination of iron and a transition metal element other than iron and the rare earth elements and x is a positive number larger than 1 varying with the rare earth element, said RxT4B4 phase having RxT4B4 grains with a grain diameter of 0.1 to 10 &mgr;m and (d) the R2T14B phase, in which R and T each have the same meaning as defined above, the R2T14B phase having R2T14B grains with a grain diameter of 0.1 to 20 &mgr;m, each phase being uniformly dispersed in the four-phase region, is in the range from 1 to 20% by volume, with the proviso that the rest of the volume fraction consists of the R-rich phase, RxT4B4 phase and R2T14B phase or consists of the R-rich phase and R2T14B phase.