Patent ID: 7985303

Claim:
A method for preparing a rare earth permanent magnet, comprising the steps of: disposing an alloy powder on a surface of a sintered body of the composition R a -T 1 b -B c wherein R is at least one element selected from rare earth elements inclusive of Y and Sc, T 1 is at least one element selected from Fe and Co, B is boron, “a,” “b” and “c” indicative of atomic percent are in the range: 12≦a≦20, 4.0≦c≦7.0, and the balance of b, said alloy powder having the composition M 1 d -M 2 e wherein each of M 1 and M 2 is at least one element selected from the group consisting of Al, Si, C, P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, and Bi, M 1 is different from M 2 , “d” and “e” indicative of atomic percent are in the range: 0.1≦e≦99.9 and the balance of d, and containing at least 70% by volume of an intermetallic compound phase, and heat treating the sintered body having the powder disposed on its surface at a temperature equal to or below the sintering temperature of the sintered body in vacuum or in an inert gas, for causing at least one element of M 1 and M 2 in the powder to diffuse to grain boundaries in the interior of the sintered body and/or near grain boundaries within sintered body primary phase grains.