Method for preparing rare earth permanent magnet material

摘要

A permanent magnet material is prepared by covering an anisotropic sintered magnet body of formula: R¹_x(Fe_1-yCo_y)_100-x-z-aB_zM_a wherein R¹ is a rare earth element, M is Al, Cu or the like, with a powder comprising an oxide of R², a fluoride of R³ or an oxyfluoride of R⁴ wherein R², R³, and R⁴ are rare earth elements, and having an average particle size up to 100 mum, heat treating the powder-covered magnet body in a hydrogen gas-containing atmosphere for inducing disproportionation reaction on R¹₂Fe₁₄B compound, and continuing heat treatment at a reduced hydrogen gas partial pressure for inducing recombination reaction to said compound, thereby finely dividing said compound phase to a crystal grain size up to 1 mum, and for effecting absorption treatment, thereby causing R², R³ or R⁴ to be absorbed in the magnet body.