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

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[Object] To provide a high-performance rare earth-based magnet exhibiting a high coercive force or a high residual magnetic flux density even when the content of a rare earth element such as Dy or the like which is scarce is reduced. [Construction] A rare earth-iron-boron based magnet includes a crystal grain boundary layer enriched in element M (M is at least one rare earth element selected from Pr, Dy, Tb, and Ho) by diffusion of the element M from the surface of the magnet, wherein the relation between the coercive force Hcj and the content of the element M in the whole of the magnet is represented by the following expression : Hcj ≥ 1 + 0.2 × M (wherein 0.05 ≤ M ≤ 10) wherein Hcj is the coercive force (unit : MA/m), and M is the content of the element M in the whole of the magnet (% by mass). Furthermore, the magnet satisfies the following expression : Br ≥ 1.68.- 0.17 × Hcj wherein Br is the residual magnetic flux density (unit : T) .