An investigation of first-order transition across charge ordered and ferromagnetic phases in Gd(0.5)Sr(0.5)MnO3 single crystals by magnetic and magnetotransport studies

Abstract

Gadolinium strontium manganite single crystals of the composition Gd(0.5)Sr(0.5)MnO(3) were grown using the optical float zone method. We report here the magnetic and magnetotransport properties of these crystals. A large magnetoresistance ∼10(9)% was observed at 45 K under the application of a 110 kOe field. We have observed notable thermomagnetic anomalies such as open hysteresis loops across the broadened first-order transition between the charge order insulator and the ferromagnetic metallic phase while traversing the magnetic field-temperature (H-T) plane isothermally or isomagnetically. In order to discern the cause of these observed anomalies, the H-T phase diagram for Gd(0.5)Sr(0.5)MnO(3) is formulated using the magnetization-field (M-H), magnetization-temperature (M-T) and resistance-temperature (R-T) measurements. The temperature dependence of the critical field (i.e. H(up), 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 anomalous according to the classical concepts of the first-order phase transition. Accordingly, H(up) values below ∼20 K are unsuitable to represent the supercooling limit. It is possible that the nature of the metastable states responsible for the observed open hysteresis loops is different from that of the supercooled ones.