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

In this paper, La0.9Sr0.1MnO3 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 La0.9Sr0.1MnO3 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 TC variation in La0.9Sr0.1MnO3 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 TC to explain quantitatively such an anomalous strain effect.