| 摘要 |
A functionally graded rare earth permanent magnet is in the form of a sintered magnet body having a composition R<SUP>1</SUP><SUB>a</SUB>R<SUP>2</SUP><SUB>b</SUB>T<SUB>c</SUB>A<SUB>d</SUB>F<SUB>e</SUB>O<SUB>f</SUB>M<SUB>g </SUB>wherein the concentration of R<SUP>2</SUP>/(R<SUP>1</SUP>+R<SUP>2</SUP>) contained in grain boundaries surrounding primary phase grains of (R<SUP>1</SUP>,R<SUP>2</SUP>)<SUB>2</SUB>T<SUB>14</SUB>A tetragonal system within the sintered magnet body is on the average higher than the concentration of R<SUP>2</SUP>/(R<SUP>1</SUP>+R<SUP>2</SUP>) contained in the primary phase grains, R<SUP>2 </SUP>is distributed such that its concentration increases on the average from the center toward the surface of the magnet body, the oxyfluoride of (R<SUP>1</SUP>,R<SUP>2</SUP>) is present at grain boundaries in a grain boundary region that extends from the magnet body surface to a depth of at least 20 mum, and the magnet body includes a surface layer having a higher coercive force than in the interior. The invention provides permanent magnets having improved heat resistance.
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