NDFEB SINTERED MAGNET, AND PROCESS FOR PRODUCTION THEREOF

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Disclosed is a NdFeB sintered magnet which can have high coercivity (HcJ) even when the sintered d magnetic has a thickness of 5 mm or more, and has a high maximum energy product ((BH)max) and a high squareness ratio (SQ). The NdFeB sintered magnet is produced by dispersing Dy and/or Tb in grain boundaries in a base material for the NdFeB sintered magnet by a grain boundary diffusion process. The NdFeB sintered magnet is characterized in that the amount of the atoms of a rare earth that are present in the base material in a metal state is 12.7 to 16.0%, a rare earth-rich phase is present continuously in an area spreading from the surface of the base material to a depth of 2.5 mm from the surface in the grain boundaries in the base material, and the grain boundaries in which RH diffused by the grain boundary diffusion process spreads to a depth of 2.5 mm from the surface.