R-T-B based sintered magnet

摘要

The present invention provides a permanent magnet with a coercivity that will not be significantly decreased and a light weight compared to conventional R-T-B based permanent magnets. A core-shell structure is formed for the major phase grain by adding Cu to the R-T-B based magnet which is the raw material. When the mass concentration of Y in the core portion is set as EY, the mass concentration of Y in the shell portion is set as LY and the mass concentration of Y in the R2—Fe14—B crystal grain calculated from the ratio R1:Y in the total composition is set as SY, the ratio α of EY to SY (EY/SY) is 1.1 or more. Thus, the magnetic insulation among the crystal grains becomes better which prevents the coercivity from decreasing due to the addition of Y. Further, the addition of Y makes the magnet lighter in weight.

主权项

1. A R-T-B based sintered magnet, wherein,
R contains Y and R1 as essential, Y is yttrium, R1 represents at least one rare earth element except Y, and T represents at least one transition metal element containing Fe or the combination of Fe and Co as essential, the R-T-B based sintered magnet comprises major phase grains with a core portion and a shell portion which covers said core portion, when the mass concentration of Y in the core portion is set as EY, the mass concentration of Y in the shell portion is set as LY and the mass concentration of Y in the R2—Fe14—B crystal grain calculated from the ratio of R1:Y in the total composition is set as SY, the ratio α of EY to SY (EY/SY) is 1.1 or more, and the R-T-B based sintered magnet contains Cu.