NdFeB sintered magnet and method for producing the same

An NdFeB sintered magnet with Dy and/or Tb diffused through grain boundaries by a grain boundary diffusion method, wherein:

• a magnet base material is a plate-shaped magnet base material having a thickness of 3.5 mm or greater;
• the magnet base material does not contain Tb;
• an amount of a rare earth in a metallic state contained in the plate-shaped magnet base material is 12.7 at % or greater;
• a total amount of O, C and N contained in the plate-shaped magnet base material is 2900 ppm or less;
• in a grain of the NdFeB sintered magnet, more Dy and/or Tb exist on a surface of the grain than inside of the grain;
• in the NdFeB sintered magnet, more Dy and/or Tb exist on a surface of the NdFeB sintered magnet than inside of the NdFeB sintered magnet;
• the NdFeB sintered magnet has a coercivity between 1.6 MA/m and 1.96 MA/m;
• the NdFeB sintered magnet has a residual flux density between 1.27 T and 1.38 T;
• and
• the NdFeB sintered magnet has a squareness value between 90% and 94%.