PROCESS FOR PRODUCTION OF NdFeB SINTERED MAGNETS AND NDFEB SINTERED MAGNETS

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The invention provides a process for the production of NdFeB sintered magnets which have higher coercive force and higher rectangularity of magnetization curve than those of conventional magnets. A process for the production of NdFeB sintered magnets which comprises forming a layer containing Dy and/or Tb on the surface of an NdFeB sintered magnet base and heating the obtained magnet precursor to a temperature not exceeding the sintering temperature of the magnet base to diffuse the Dy and/or Tb contained in the layer to the inside of the magnet base through grain boundaries of the base, characterized in that : (a) the content of metallic rare earth elements in the magnet base is 12.7at% or above, (b) the layer is a powder layer formed by the accumulation of a powder, and (c) the powder layer contains metallic Dy and/or Tb in an amount of 50mass% or above.