NdFeB-BASED SINTERED MAGNET

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The purpose of the present invention is to provide an NdFeB-based sintered magnet which is less susceptible to irreversible demagnetization under a high-temperature atmosphere or heat-buildup. This NdFeB-based sintered magnet is a magnet which is manufactured by preparing a base material from an NdFeB-based alloy powder through both orientation in a magnetic field and sintering, making Dy and/or Tb adhere to the surface of the base material, and subjecting the resulting base material to grain boundary diffusion treatment to diffuse the Dy and/or Tb into the grain boundaries in the base material, and which is characterized by having a squareness ratio of 95% or more. The NdFeB-based sintered magnet can be manufactured by : using, as the starting alloy, an NdFeB-based alloy in which lamellas of a rare earth-rich phase are dispersed at prescribed intervals nearly uniformly; making the alloy occlude hydrogen; preparing a base material for an NdFeB-based sintered magnet from the resulting alloy in a manner such that the heating for desorbing the occluded hydrogen is not conducted prior to a sintering step; and subjecting the base material to grain boundary diffusion treatment.