Unusual magnetic transitions and phonon instabilities in tetragonal SrIrO3 under epitaxial strain

Abstract

A recent study has demonstrated the cutting-edge techniques in applying large strains to the transition metal perovskite oxides up to 8%. In order to explore the unknown magnetic phase diagrams and physical properties of the perovskite SrIrO3, we employ first principles density-functional theory calculations to study the magnetic, electronic and dynamical properties of tetragonal SrIrO3 under epitaxial strains. There are four abrupt changes in the magnetic moment of Ir atom with in-plane epitaxial strain changing from −10% to +7% (positive/negative value corresponds to the tensile/compressive strain) relative to the cubic phase. In particular, under an in-plane compressive strain of ~1.5% or tensile strain of ~1%, a weak ferromagnetic to strong ferromagnetic transition is induced, whereas for a compressive strain lager than 7.7% or a tensile strain larger than 4.7%, the magnetic moment of Ir drops gradually with the increase of the strain. These magnetic transitions can be qualitatively explained by the Stoner model. In addition, the phonon instabilities of tetragonal SrIrO3 under both compressive and tensile strains are revealed by lattice dynamics calculations. These phonon instabilities of tetragonal SrIrO3 show potential polar metal behaviors which are similar to those found in tetragonal SrRuO3. This may stimulate further investigation in the properties of SrIrO3-based complex oxide interfaces.