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

Abstract

The structural, magnetic and transport properties of La₀.₇ (Ca₁₋ySry)₀.₃ MnO₃ 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 (R c3 ) 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 La₀.₇ (Ca₁₋ySry)₀.₃ MnO₃ thin-film system is presented.