Patent ID: 8187392

Claim:
A method for producing an R—Fe—B based rare-earth sintered magnet, the method comprising the steps of: (a) providing an R—Fe—B based rare-earth sintered magnet body, which 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; (b) diffusing a heavy rare-earth element RH (which is at least one element selected from the group consisting of Dy, Ho and Tb) inside the R—Fe—B based rare-earth sintered magnet body; and (c) removing a surface portion of the R—Fe—B based rare-earth sintered magnet body, in which the heavy rare-earth element RH has been diffused, to a depth of 5 μm to 500 μm, wherein the step (b) includes the steps of: (b1) arranging a bulk body including the heavy rare-earth element RH (which is at least one element selected from the group consisting of Dy, Ho and Tb), along with the R—Fe—B based rare-earth sintered magnet body, in a processing chamber and arranging the bulk body and the R—Fe—B based rare-earth sintered magnet body out of contact with each other in the processing chamber and leaving an average gap of 0.1 mm to 300 mm between them; and (b2) heating the bulk body and the R—Fe—B based rare-earth sintered magnet body together to a temperature of 700° C. to 1,000° C., thereby diffusing the heavy rare-earth element RH inside the R—Fe—B based rare-earth sintered magnet body while simultaneously supplying the heavy rare-earth element RH from the bulk body onto the surface of the R—Fe—B based rare-earth sintered magnet body.