Magnetic and electronic phase separation driven by structural clustering in La0.7 (Ca1-y Sry)0.3MnO3 thin films

Анотація

The structural, magnetic and transport properties of La_0.7 (Ca_1-y Sr_y)_0.3MnO₃ films deposited on LaAlO₃ (001) single-crystalline substrate by rf-magnetron sputtering using «soft» (or powder) targets are investigated. It was found that at 0.3 ≤ y ≤ 0.5 both rhombohedral (R̅3c) and orthorhombic (Pnma) crystal phases are coexistent at room temperature, forming a nanoclustered microstructure. The clustered films manifest the two-stage magnetic and electronic transition, which are typical for the phase-separated systems. It was shown that for 0.5≥ y ≥0 the nonlinear (almost parabolic) field-dependent magnetoresistance is typical at room temperature while for 0.65≤ y ≤1.0 its transform to the linear behavior. The magnetotransport properties of the films are explained within the framework of a field-dependent activation energy model. The magnetic phase diagram for the La_0.7 (Ca_1-y Sr_y)_0.3MnO₃ thin-film system is presented.