Angular dependence of coercivity in Pr---Fe---B sintered magnets

Hysteresis loops were measured for varying angles of the applied field at different temperatures in oriented sintered magnets of compositions Fe₇₅Pr₁₇B₈ and Fe₅₃Pr₁₇B₃₀. While at elevated temperatures the coercive field increases monotonically with the angle of the applied field, a minimum in the angular dependence is found below room temperature. The temperature dependence of coercivity for the field applied parallel and with an angle of 45° to the alignment direction is well described by a nucleation model in the whole temperature range. The results are compared to Fe---Nd---B magnets, showing that the occurrence of a minimum in the angular dependence is related to the ratio of the experimental to the theoretical coercive fields.