Appearance of glassy ferromagnetic behavior in [formula omitted] ([formula omitted]) thin films: A revised phase diagram

Abstract

We report on results of electrical transport properties of Gd1-xCaxMnO3 (0⩽x⩽1) thin films fabricated on top of SrTiO3 substrates by pulsed laser deposition. The lowest studied doping level (x<0.1) was enough to trigger a transition from the antiferromagnetic state present in the parent compound (x = 0) to a ferrimagnetic state. Up to x = 0.3, the system exhibits a high temperature insulator paramagnetic state and a low temperature insulator ferrimagnetic one. At higher concentrations, the electrical and magnetical properties of the films differ drastically from the bulk form which shows a strong antiferromagnetic behavior. At mid Ca substitution (0.4⩽x⩽0.7), samples show a high temperature charge ordered state with ordering temperatures around room temperature and a low temperature glassy state which was not observed in their bulk counterparts. In contrast, high x samples show a high temperature conductive paramagnetic state and a low temperature insulator antiferromagnetic phase. More interestingly, sample x = 0.9 shows a distinct minimum in the resistivity versus temperature plots and a region of thermal hysteresis which indicate a first order transition. Magnetoresistance measurements display a strong irreversibility which we attributed to phase separation effect of a kinetically arrested ferromagnetic metallic phase and a stable antiferromagnetic insulator phase. Based on the above observations and previous magnetic results, we have reconstructed a phase diagram and characterized the properties of each phase.