Anomalous temperature dependence of coercivity in precipitation hardened Pr-Co-Cu-Ti magnets

The anomalous temperature dependence of coercicity, H-c(T), has been observed in precipitation hardened PrCo6.7-xCuxTi0.3 (x=0.2-1) magnets. Transmission electron microscopy reveals that they exhibit a cellular microstructure. With an increase of Cu content, the Curie temperature of the 2:17 phase remains nearly unchanged whereas that of the 1:5 phase decreases. The peak of H-c(T) becomes higher, broader and shifts towards low temperature while the room temperature coercivity remains low and does not change with an increase of Cu content. There is a strong correlation between the Curie temperature of the 1:5 phase and the peak of H-c(T). The effect of Cu on H-c(T) cannot be explained by a traditional domain wall pinning model. It is highly likely that their magnetization reversal is controlled by the nucleation of reverse domains in isolated 2:17 cells. (C) 2003 American Institute of Physics.