稀土族永久磁体

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A rare earth permanent magnet is in the form of a sintered magnet body having a composition R1a R2b Tc Ad Fe Of Mg wherein F and R2 are distributed such that their concentration increases on the average from the center toward the surface of the magnet body, the concentration of R2 /(R1 ＋R2 ) contained in grain boundaries surrounding primary phase grains of (R1 , R2 )2 T14 A tetragonal system within the sintered magnet body is on the average higher than the concentration of R2 /(R1 ＋R2 ) contained in the primary phase grains, and the oxyfiuoride of (R1 , R2 ) is present at grain boundaries in a grain boundary region that extends from the magnet body surface to a depth of at least 20 μm. The invention provides R－Fe－B sintered magnets which exhibit high magnet performance despite minimal amounts of Tb and Dy used.