Strain-dependent magnetism and electric transport properties of La0.7Sr0.3CoO3 films

The electronic and magnetic properties of some perovskite-type 3d transition metal oxides are known to be sensitive to epitaxial strain. In order to investigate the influence of strain in La0.7Sr0.3CoO3 (LSCO) compound, epitaxial films under different biaxial strain have been grown using various substrates. Additionally, piezoelectric substrates of the composition 0.72PbMg1/3Nb2/3O3-0.28PbTiO3 (PMN-28%PT) were employed to control the in-plane strain dynamically by applying an electrical field. An insulator-type behaviour was observed in films grown under tensile strain, whereas compressed films show bulk, metallic properties. This drastic influence of strain was confirmed by using the PMN-PT substrates, where a reversible strain of 0.15% caused a resistance change of one order of magnitude at room temperature. On the contrary, the magnetization data revealed a rather small impact of tensile strain on the magnetic behaviour of LSCO films. We suggest that the insulator state of La0.7Sr0.3CoO3 is caused by a stain-induced static Jahn-Teller-type deformation of the CoO6 units, which may be efficient as a localization mechanism