Patent ID: 8182619

Claim:
An R—Fe—B based rare-earth sintered magnet comprising, 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, wherein the magnet further includes a metallic element M and a heavy rare-earth element RH, both of which have been introduced from a surface of the magnet by grain boundary diffusion into an interior of the magnet, the metallic element M being at least one element that is selected from the group consisting of Al, Ga, In, Sn, Pb, Bi, Zn and Ag, the heavy rare-earth element RH being at least one element that is selected from the group consisting of Dy, Ho and Tb, wherein the heavy rare-earth element RH is diffused to a depth of about 0.5 mm or more as measured from a surface of the magnet, and wherein each crystal grain of the R 2 Fe 14 B type compound has an outer periphery layer in which the heavy rare-earth element RH is more concentrated than in the interior of the crystal grain.