A method of manufacturing a sintered NdFeB magnet

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PROBLEM TO BE SOLVED : To provide a manufacturing method of a NdFeB sintered magnet with high coercive force and high square-shape property for the magnetization curve.SOLUTION : The manufacturing method of the NdFeB sintered magnet comprises a grain boundary diffusion treatment. In the grain boundary diffusion treatment, Dy and/or Tb in a layer comprising Dy and/or Tb are diffused to an inner part of a magnet base through a crystal grain boundary of the magnet base, by forming the layer on a surface of the NdFeB sintered magnet base, and heating it to a temperature of not higher than the sintering temperature of the magnet base; a rare earth amount in a metal state, which is included in the magnet base, is not less than 12.9 atom%; and the layer comprises fluoride of Dy and/or fluoride of Tb of not lower than 50 mass%. Even if the magnet has a thickness of 3-6 mm which is difficult for improvement of a characteristic in conventional cases, the NdFeB sintered magnet having high coercive force of not lower than 1.4 mA/m and high square-shape property of the magnetization curve can be manufactured.