Theoretical Study of the Epitaxial Strain Effect on the Structural and Magnetic Properties of a YFeO₃ Thin Film on a SrTiO₃ Substrate

The electronic structure and magnetic properties of a YFeO₃ thin film deposited on a SrTiO₃ substrate are studied using the GGA+U method. It is shown that the epitaxial strain in the YFeO₃/SrTiO₃ thin film significantly changes the crystal structure and displaces iron atoms located at the film surface from the plane formed by the nearest oxygen atoms. These distortions lead to a change in the type of long-range magnetic ordering from the G-type antiferromagnetic ordering observed in stoichiometric YFeO₃ to ferrimagnetic ordering close to the A-type antiferromagnetism and to the transition from the insulating state to metallic one. The complete relaxation of atomic positions gives rise to a “breathing mode” distortion in the film bulk, which is accompanied by the electric polarization of 15.1 μC/cm². The latter is in agreement with the experiment. The distortion of oxygen octahedra surrounding iron atoms leads to the transition from the high-spin state to the intermediate-spin state and to a stepwise decrease in local magnetic moments.