R-T-B BASED PERMANENT MAGNET

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An R-T-B based permanent with the residual magnetic flux density Br2 satisfies the relationship of Br2/Br≧0.90, wherein the residual magnetic flux density Br2 is obtained after applying the external magnetic field of Hex and then applying an external magnetic field of 0.95 HcJ. Such a R-T-B based permanent magnet preferably contains main phase grains with a composition of (R11-xR2x)2T14B (R1 is rare earth element(s) composed of one or more elements selected from the group consisting of Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, R2 is element(s) containing at least one selected from the group consisting of Y, La and Ce, T is one or more transition metal elements including Fe or a combination of Fe and Co as essential elements, and 0.2≦x≦0.7) and thus can be suitably used as a magnet with a variable magnetic force for a variable magnetic flux motor.