Mechanism of the anomalous temperature dependence of coercivity in Sm(Co,Fe,Cu,Zr)[subscript]z high-temperature magnets

Abstract

Coercivity mechanism of the precipitation-hardened Sm(Co,Fe,Cu,Zr)z high-temperature magnets was found to vary with temperature by measurements of reversible magnetization. The magnetization reversal is mainly controlled by domain-wall pinning when temperature is lower than 800 K, while is mainly dominated by nucleation at higher temperature. It is interesting to find that the anomalous temperature dependence of coercivity Hc(T) near Curie temperature of the 1:5 phase is caused by the fast drop of intergranular exchange coupling. This mechanism can also explain the coercivity behavior that the anomalous Hc(T) tends to disappear with increasing z value.