An investigation of first-order transition across charge ordered and ferromagnetic phases inGd0.5Sr0.5MnO3 single crystals by magnetic and magnetotransport studies

Abstract

Gadolinium strontium manganite single crystals of the compositionGd0.5Sr0.5MnO3 were grown using the optical float zone method. We report here the magneticand magnetotransport properties of these crystals. A large magnetoresistance∼109% was observed at 45 K under the application of a 110 kOe field. We have observednotable thermomagnetic anomalies such as open hysteresis loops across thebroadened first-order transition between the charge order insulator and theferromagnetic metallic phase while traversing the magnetic field–temperature (H–T)plane isothermally or isomagnetically. In order to discern the cause of these observed anomalies, theH–T phasediagram for Gd0.5Sr0.5MnO3 is formulated using the magnetization–field (M–H), magnetization–temperature (M–T) andresistance–temperature (R–T) measurements. The temperature dependence of the critical field (i.e. Hup, the field required for transformation to the ferromagnetic metallic phase) is non-monotonic.We note that the non-monotonic variation of the supercooling limit is anomalousaccording to the classical concepts of the first-order phase transition. Accordingly,Hup valuesbelow ∼20 K are unsuitable to represent the supercooling limit. It is possible that the nature of themetastable states responsible for the observed open hysteresis loops is different from that ofthe supercooled ones.