Patent ID: 7922832

Claim:
A method for preparing a permanent magnet material, comprising the steps of: providing an anisotropic sintered magnet body having the compositional formula: R x (Fe 1-y Co y ) 100-x-z-a B z M a wherein R is at least one element selected from rare earth elements inclusive of Sc and Y, M is at least one element selected from the group consisting of Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, and W, x, y, z, and a indicative of atomic percentage are in the range: 10≦x≦15, 0≦y≦0.4, 3≦z≦15, and 0≦a≦11, said magnet body containing a R 2 Fe 14 B compound as a primary phase, machining the magnet body to a specific surface area of at least 6 mm −1 , heat treating the magnet body which has been machined in a hydrogen gas-containing atmosphere at 600 to 1,100° C., for inducing disproportionation reaction on the R 2 Fe 14 B compound, continuing the heat treatment in an atmosphere having a reduced hydrogen gas partial pressure at 600 to 1,100° C., for inducing recombination reaction to the R 2 Fe 14 B compound, thereby finely dividing the R 2 Fe 14 B compound phase to a crystal grain size equal to or less than 1 μm, and washing the magnet body with at least one agent of alkalis, acids and organic solvents, after the recombination reaction treatment.