Metal-insulator transition in epitaxial films of LaMnO3 manganites grown by magnetron sputtering

We have studied thin films of LaMnO3 manganite grown by RF magnetron sputtering at high pressure on crystalline substrates with cubic symmetry. It is established that these films exhibit a metal-insulator transition, whereas LaMnO3 grown on orthorhombic substrates remains in a dielectric state. The parameters of the metal-insulator transition have been studied as dependent on the level and symmetry of mechanical stresses that arise during the epitaxial growth of LaMnO3 films on various substrates. The resistance of LaMnO3 films grown on SrTiO3 substrates has been studied as a function of the film thickness. It is found that the presence of excess oxygen due to substitution in the cation system can significantly influence the Mn4+/Mn3+ ion ratio in the film and thus lead to the appearance of the metal-insulator transition.