Patent ID: 8206516

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 including, as a main phase, crystal grains of an R 2 Fe 14 B type compound that includes a light rare-earth element RL, which is at least one of Nd and Pr, as a major rare-earth element R; (b) arranging a bulk body including a 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 container; and (c) heating the container, by a heat treatment furnace in which the container is loaded, so that the bulk body and the R—Fe—B based rare-earth sintered magnet body arranged in the container are heated to a temperature of 700° C. to 1,000° C. to vaporize the heavy rare-earth element RH from the bulk body, thereby diffusing the heavy rare-earth element RH into the R—Fe—B based rare-earth sintered magnet body while supplying the heavy rare-earth element RH from the bulk body to the surface of the R—Fe—B based rare-earth sintered magnet body so that substantially no thin film made of the heavy rare-earth element RH is formed on the R—Fe—B based rare-earth sintered magnet body, wherein the step (c) includes arranging the bulk body and the R—Fe—B based rare-earth sintered magnet body out of contact with each other in the container and setting an average gap between the two bodies within the range of 0.1 mm to 300 mm, and wherein the step (c) includes setting a difference in temperature between the R—Fe—B based rare-earth sintered magnet body and the bulk body within 20° C.