Patent ID: 8945318
Filing Date: 2015-02-03
Classification: B22F,C22C,H01F

Abstract:
1. An R—Fe—B based rare-earth sintered magnet comprising an R—Fe—B based rare-earth sintered magnet body that includes, as a main phase, crystal grains of an R 2 Fe 14 B type compound, including a light rare-earth element RL, which is at least one of Nd and Pr, as a major rare-earth element R, and a heavy rare-earth element RH, which is at least one element selected from the group consisting of Dy, Ho and Tb, wherein at a depth of 20 μm under the surface of the R—Fe—B based rare-earth sintered magnet body, the crystal grains of the R wherein at a depth of 500 μm under the surface of the R—Fe—B based rare-earth sintered magnet body, the crystal grains of the R wherein the surface of the R—Fe—B based rare-earth sintered magnet body is a machined surface that is not covered with a metal layer of the heavy rare-earth element RH and that is a surface of the R—Fe—B based rare-earth sintered magnet body, from which its surface portion has already been removed after the heavy rare-earth element RH has been introduced into the R—Fe—B based rare-earth sintered magnet body from outside of the R—Fe—B based rare-earth sintered magnet body, wherein the R—Fe—B based rare-earth sintered magnet body has a size of 1 mm to 4 mm as measured in a thickness direction, wherein a difference ΔH wherein the magnet has an RH-RL-O compound in at least one grain boundary triple junction, which is located at a depth of 100 μm or less under the surface of the R—Fe—B based rare-earth sintered magnet body.