Thickness dependent structural, magnetic and magneto-transport properties of epitaxial Nd_0.50Sr_0.50MnO₃ thin films

We report the thickness-dependent structural, magnetic and magneto-transport properties in epitaxial Nd_0.50Sr_0.50MnO₃ thin films (10 to 300nm) prepared by DC magnetron sputtering technique on single crystalline (001) oriented substrate LaAlO₃. X-ray diffraction pattern reveals the epitaxial growth of all the films and the out-of-plane lattice parameter of films were found to increase with thickness. As thickness of the film increases the paramagnetic insulator (PMI) to ferromagnetic metal (FMM) transition temperature (T_C), charge ordered transition temperature (T_CO) and magnetic moment were found to increase with a strong bifurcation in ZFC-FC magnetization. The asymmetry in the coercivity seen in field dependent magnetization loops (M-H loops) suggests the presence of exchange bias (EB) effect. While temperature dependent resistivity of films show the semiconducting nature for thickness 10-200nm in temperature range from 5-300K, the film of thickness 300nm shows the insulator to metal transition with transition temperature (T_IM) at 175K. Temperature dependent low field magnetoresistance (LFMR) measured at 4kOe found to decrease with thickness and for high field magnetoresistance (HFMR) at 40kOe and 60kOe also show similar dependence and a crossover at intermediate temperature range in the magnitude of MR between 10nm and 200nm films at constant field. Colossal increase in magnetoresistance observed for 10nm film at low temperature.