Anomalous magnetoresistance of nonequilibrium Eu-TM (Co, Mo) alloy thin films

We studied the magnetization and magnetoresistance ratio (MR) of nonequilibrium Eu-rich Eu-Tm (Tm=Co, Mo) alloy thin films prepared by vapour-phase synthesis. We observed that the magnetization curves of the Eu-TM films show an irreversible kink at about 8 T. The longitudinal and transverse MR curves of these films also exhibit irreversible positive-to-negative change at about 8 and 4 T, respectively, while reversible components show only a monotonic decrease. These behaviours are in contrast with the monotonically increasing MR of pure Eu, measured up to 14 T, but are essentially identical to those observed for nonequilibrium Eu-Fe thin films, implying that the anomaly results from structural disorder rather than from the magnetic moments of impurities. (author)