Patent ID: 8695210

Claim:
A method for preparing a sintered Nd base magnet comprising in the recited order, the steps of: providing a sintered Nd base magnet block having surfaces perpendicular to a magnetization direction and extending to the magnetization direction; coating the surfaces of the magnet block excluding the surface perpendicular to the magnetization direction with a Dy or Tb oxide powder, a Dy or Tb fluoride powder, or a Dy or Tb-containing alloy powder, thereby obtaining a coated block; heating the coated block so that the Dy or Tb in the Dy or Tb oxide powder, the Dy or Tb fluoride powder, or the Dy or Tb-containing alloy powder, diffuses into the block; cutting the coated block in a plane perpendicular to the magnetization direction to form a cut section into a magnet segment having a coercive force distribution on the cut section so that the coercive force is high at a periphery of the cut section and lower toward an inside of the cut section and a constant coercive force distribution in the magnetization direction; and then machining the magnet segment on the surface perpendicular to the magnetization direction so as to make a cross-section along the magnetization direction into a C or D shape.