Patent ID: 7955443

Claim:
A method for preparing a permanent magnet material, comprising the steps of: providing an anisotropic sintered magnet body having the compositional formula: R 1 x (Fe 1-y Co y ) 100-x-z-a B z M a wherein R 1 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 1 2 Fe 14 B compound as a primary phase, machining the magnet body to a specific surface area of at least 6 mm −1 , disposing on a surface of the machined magnet body a powder comprising at least one of an oxide of R 2 , a fluoride of R 3 , and an oxyfluoride of R 4 wherein each of R 2 , R 3 , and R 4 is at least one element selected from rare earth elements inclusive of Sc and Y, and having an average particle size equal to or less than 100 μm, wherein R 2 , R 3 , or R 4 contains at least 10 atom % of Dy and/or Tb, and the total concentration of Nd and Pr in R 2 , R 3 or R 4 is lower than the total concentration of Nd and Pr in R 1 , heat treating the machined magnet body having the powder disposed on its surface in a hydrogen gas-containing atmosphere at 600 to 1,100° C. for inducing disproportionation reaction on the R 1 2 Fe 14 B compound, and continuing 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 1 2 Fe 14 B compound, thereby finely dividing the R 1 2 Fe 14 B compound phase to a crystal grain size equal to or less than 1 μm, and for effecting absorption treatment, thereby causing at least one of R 2 , R 3 , and R 4 in the powder to be absorbed in the magnet body.