Strain-induced Curie temperature variation in La0.9Sr0.1MnO3 thin films

Abstract

In this paper, La_0.9Sr_0.1MnO₃ thin films were grown epitaxially on SrTiO₃, LaAlO₃ and MgO substrates, and their structural, electrical and magnetic properties were investigated, aiming at revealing and explaining the strain effects on the physical properties of La_0.9Sr_0.1MnO₃ films. Compared with the compressive strained film on LaAlO₃, the tensile strained films show a higher or lower Curie temperature when grown on SrTiO₃ or MgO. The films on SrTiO₃ and LaAlO₃ show ferromagnetic metallic state at low temperature, while a ferromagnetic insulating state is observed in that on MgO. More valuably, significant enhanced magnetoresistance around room temperature is observed in the films grown on SrTiO₃ and LaAlO₃. The strain-induced T_C variation in La_0.9Sr_0.1MnO₃ films could not be explained by double-exchange mechanism alone, and the strong electron-phonon coupling originating from Jahn–Teller distortion of the MnO₆ octahedra should be also taken into consideration. Based on this, we successfully derive a simplified equation for T_C to explain quantitatively such an anomalous strain effect.