METHOD FOR PRODUCING RARE EARTH PERMANENT MAGNET MATERIAL

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A method for preparing a rare earth permanent magnet material is characterized by comprising the steps of disposing a powder mixture on a surface of a sintered magnet body of R1-Fe-B composition wherein R1 is at least one element selected from rare earth elements inclusive of Sc and Y, the powder mixture comprising a powder containing at least 0.5% by weight of M which is at least one element selected from Al, Cu, and Zn and having an average particle size equal to or less than 300 µm and a powder containing at least 30% by weight of a fluoride of R2 which 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, and heat treating the magnet body having the powder disposed on its surface at a temperature equal to or below the sintering temperature of the magnet body in vacuum or in an inert gas, for causing at least one of M and R2 in the powder mixture to be absorbed in the magnet body. The invention provides an R-Fe-B sintered magnet with high performance and a minimized amount of Tb or Dy used.