Patent ID: 7824506

Claim:
A method for modifying grain boundaries of a Nd—Fe—B base magnet comprising: placing a Nd—Fe—B base sintered magnet body in contact with a compound selected from a fluoride, an oxide, or a chloride of an M metal element (where M is Pr, Dy, Tb, or Ho); reducing the compound of M metal element by using a chemical reducing agent selected from the group consisting of Ca metal, Mg metal or a hydride thereof such that M metal element deposits on the Nd—Fe—B base sintered magnet body; and keeping the Nd—Fe—B base sintered magnet body at a temperature in a range of 800° C. to 1100° C., wherein the M metal element to diffuse and penetrate from a surface of the Nd—Fe—B base sintered magnet body having a Nd-rich crystal grain boundary phase surrounding principal Nd 2 Fe 14 B crystals to the grain boundary phase.