Structure, magnetism and electrical transport in epitaxial La0.23Pr0.41Ca0.36MnO3 thin films: Consequences of film thickness

A systematic study of the consequences of in-plane tensile strain on the correlation between structure/microstructure and magneto-electrical properties of La0.23Pr0.41Ca0.36MnO3/SrTiO3 (001) thin films is performed. At lower film thickness (d≤27 nm) the dominant tensile strain supports layered morphology. At d=41 nm structural/microstructural crossover takes place and at d≥41 nm relaxation induced tilt and dilations of the lattice generate defects like dislocations, which in turn transforms the layer by layer growth into disordered brick type morphology. It appears that the relaxation even at higher thickness (∼81 nm) is partial only and the strain may have a self-sustained nature. The domination of the tensile strain suppresses the ferromagnetic-metallic phase due to the possible electronic reconstruction which could give rise to a magnetically disordered insulator ‘dead’ layer and a sizeable non-magnetic insulator state at d≤27 nm. In this thickness regime the possible selective orbital stabilization could also contribute to carrier localization. At d≥41 nm the severity of the impact of the interfacial electronic reconstruction is reduced with concomitant relaxation of the tensile strain which favors carrier delocalization and yields well defined metallic-ferromagnetic phase transitions. The hysteretic nature of the phase transitions reflects the thermal cycle dependent nature of the metallic-ferromagnetic and insulating antiferromagnetic phases in this strongly phase separated material.