RARE EARTH - IRON - BORON BASED MAGNET AND METHOD FOR PRODUCTION THEREOF

[PROBLEM] To provide a high performance rare earth based magnet, characterized in that it exhibits a high coercive force or a high remanent magnetic flux density even when it has a reduced content of a rare earth element such as Dy, which is scarce. [CONSTITUTION] A rare earth - iron - boron based magnet, characterized in that it has a grain boundary layer being enriched in M element [wherein M represents one or more of rare earth elements selected from among Pr, Dy, Tb and Ho] by the diffusion of the M element from the surface of the magnet, and that a coercive force Hcj and the content of M element in the whole of a magnet satisfies the following formula : Hcj ≥ 1 + 0.2 X M [wherein 0.05 ≤ M ≤ 10, Hcj represents a coercive force in the unit of MA/m, and M represents the content of M in the whole of a magnet in mass %]; and the above magnet further characterized in that it satisfies the following formula : Br ≥ 1.68 - 0.17 X Hcj [wherein Br represents a remanent magnetic flux density in the unit of T].