Glass component induced hysteresis/memory effect in magnetoresistance of Pr 0.9Sr 0.1CoO 2.99

Abstract

Pr 1− x Sr x CoO 3− δ exhibits magnetoresistivity (MR) of up to 40% at 5 K with a strong hysteresis/memory effect. Magnetization measurements on Pr 0.9Sr 0.1CoO 2.99 in an applied field of 100 Oe show that, as temperature decreases, the zero field-cooled (ZFC) and field-cooled (FC) magnetization curves branch clearly at 50 K, and a cusp appears in the ZFC branch at T cusp∼20 K. Magnetization measurements in various fields between 100 and 10,000 Oe show that both the ZFC–FC branching temperature and, T cusp, decrease with increasing field. The magnetization-field isotherms at 5 and 10 K show hysteresis loops typical of ferromagnets. No appreciable MR is seen in this compound at 50 K, i.e. at a temperature close to ZFC–FC branching temperature. At 20 K, negative MR of above 16% is observed without any hysteresis effect. We believe that the appearance of a ferromagnetic component at 5 K and 10 K (i.e. at temperatures below T cusp) within the spin glass state of Co spins is responsible for both large MR and the prominent hysteresis/memory effect in MR.