Anomalous temperature dependence of coercivity and reversal mechanism in bulk-hardened rare earth-cobalt magnets

The “anomalous” nonmonotonic temperature dependence of coercivity, reported in Sm–Zr–Co–Cu magnets, has also been observed in bulk-hardened Y–Zr–Co–Fe–Cu alloys with a similar microstructure. The phenomenon appears to be universal for all R–Co magnets (R=rare earth) having a microstructure consisting of R2Co17 cells surrounded by the RCo5 phase. The effect of R and Cu on the temperature dependence of coercivity cannot be simply explained by traditional domain-wall pinning model based on the difference in a domain wall energy. Possibility that the coercivity is controlled by nucleation of reversed domains in magnetically isolated R2Co17 cells is discussed.