R-t-b based rare earth permanent magnet and method for production thereof

An R-T-B system rare earth permanent magnet, which comprises a sintered body comprising at least:

• main phase grains comprising R2T14B compounds (wherein R represents one or more rare earth elements, providing that the term “rare earth element” include Y (yttrium), and T represents one or more transition metal elements essentially containing Fe, or Fe and Co);
• and a grain boundary phase having a higher amount of R than said main phase grains,
• which is characterized in that said sintered body satisfies the following formulas:
• AVE(X)/Y=0.8 to 1.0;
• and
• (X/Y)max/(X/Y)min=2.0 to 13.0,
• wherein X represents (the weight ratio of heavy rare earth elements)/(the weight ratio of all the rare earth elements) for a given number of said main phase grains in said sintered body;
• Y represents (the weight ratio of heavy rare earth elements)/(the weight ratio of all the rare earth elements) for said sintered body as a whole;
• AVE(X) represents the mean value of X obtained for the given number of said main phase grains;
• (X/Y)min represents the minimum value of (X/Y) obtained for the given number of said main phase grains;
• and
• (X/Y)max represents the maximum value of (X/Y) obtained for the given number of said main phase grains.