Effect of ferroelectric-poling-induced strain on the phase separation and magnetotransport properties of La₀.₇Ca₀.₁₅Sr₀.₁₅MnO₃thin films grown on ferroelectric single-crystal substrates

Abstract

We report the effects of the ferroelectric-poling-induced strain on the phase separation, magnetic, and magnetotransport properties of La₀.₇Ca₀.₁₅Sr₀.₁₅MnO₃(LCSMO) thin films grown on ferroelectric 0.67Pb(Mg₁/₃Nb₂/₃)O₃-0.33PbTiO₃(PMN-PT) single-crystal substrates. In situ x-ray diffraction measurements show that the ferroelectric poling induces a reduction in the in-plane tensile strain in the LCSMO film, which gives rise to a decrease in the resistance and an increase in the ferromagnetism and Curie temperature Tc. The induced reduction in the tensile strain leads to opposite effect on the magnetoresistance below and above Tc. Based on a phenomenogical model that well reproduces the essential features of the field- and temperature-dependence of the resistance of the LCSMO film when the PMN-PT substrate is in unpoled and poled state, respectively, we found that the volume fraction of the ferromagnetic metallic phase is significantly enhanced due to the reduction in the in-plane tensile strain in the film. We discuss these strain effects within the framework of the electron-lattice coupling and phase separation scenario that are relevant to the strain induced by the ferroelectric poling.