Patent attributes
A rare earth permanent magnet is in the form of a sintered magnet body having a composition R1aR2bTcAdFeOfMg 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)2T14A 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 oxyfluoride 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.
