Method for producing sintered r-t-b based magnet and diffusion source

A method for producing a sintered R-T-B based magnet, comprising:

• providing a sintered R1-T-B based magnet work (where R1 is a rare-earth element;
• T is Fe, or Fe and Co);
• providing a powder of an alloy in which a rare-earth element R2 accounts for 40 mass % or more of the entire alloy, the rare-earth element R2 always including at least one of Dy and Tb;
• subjecting the alloy powder to a heat treatment at a temperature which is not lower than a temperature that is 250° C. below a melting point of the alloy powder and which is not higher than the melting point, to obtain a diffusion source from the alloy powder;
• and
• placing the sintered R1-T-B based magnet work and the diffusion source in a process chamber, and heating the sintered R1-T-B based magnet work and the diffusion source to a temperature which is not higher than a sintering temperature of the sintered R1-T-B based magnet work, to allow the at least one of Dy and Tb contained in the diffusion source to diffuse from the surface into an interior of the sintered R1-T-B based magnet work, wherein
• the alloy powder is a powder produced by atomization.