METHOD FOR PREPARING RARE EARTH PERMANENT MAGNET MATERIAL

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A process for producing a rare-earth permanent magnet material which comprises : repeatedly subjecting a sintered magnetic object having the composition R1aTbAcMd (wherein R1 is any of the rare earth elements including Sc and Y; T is Fe and/or Co; A is B (boron) and/or C (carbon); and M is Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, or W) and a powder comprising the oxide of R2, the fluoride of R3, and the oxofluoride of R4 (R2, R3, and R4 each is any of the rare earth elements including Sc and Y) and having an average particle diameter of 100 μm or smaller to a heat treatment two or more times at a temperature not higher than the sintering temperature of the magnetic object while keeping the powder present on the surface of the sintered magnetic object to thereby cause the R2, R3, and R4 contained in the powder to be absorbed in the magnetic object. By the process, a rare-earth permanent magnet material for use as an R-Fe-B sintered magnet can be produced which has high performances and is reduced in the content of Tb or Dy.© KIPO & WIPO 2009