US Patent 9044810 Rare earth magnet and its preparation

A rare earth magnet is prepared by disposing a R1-T-B sintered body comprising a R12T14B compound as a major phase in contact with an R2-M alloy powder and effecting heat treatment for causing R2 element to diffuse into the sintered body. The alloy powder is obtained by quenching a melt containing R2 and M. R1 and R2 are rare earth elements, T is Fe and/or Co, M is selected from B, C, P, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pt, Au, Pb, and Bi.