Density-functional theory calculation of magnetic properties of BiFeO3 and BiCrO3 under epitaxial strain

Abstract

This work uses density-functional theory to model the magnetic properties of bismuth-based perovskite oxides under epitaxial strain. We augment the known transition in BiFeO3 between rhombohedral-like and tetragonal-like phases occurring at 4.2% compressive epitaxial strain with the variation in magnetic behavior near this boundary. This phase boundary coincides with a transition from G- to C-type magnetic order, as well as with a 90% decrease in the magnitude of the [001]-oriented coupling coefficients. The magnitude of iron magnetization is shown to vary by no more than 3% over the entire range of compressive strain considered. In the BiCrO3 system, we report a variation in chromium magnetization of over 20%, along with transitions from bulk G-type to regions of C-type order under tensile epitaxial strain and to F-type order under both tensile and compressive epitaxial strains. The region of F-type order stabilized under compression beyond 7.9% epitaxial strain corresponds to a “super-tetragonal” phase structurally similar to the well-known phase of BiFeO3 exhibiting spontaneous polarization on the order of 150 μC/cm2.