Structural effects on the spin-state transition in epitaxially strainedLaCoO3films

Abstract

Using density-functional theory within the $\text{LSDA}+U$ method, we investigate the effect of strain on the spin state and magnetic ordering in perovskite lanthanum cobaltite, ${\text{LaCoO}}_{3}$. We show that, while strain-induced changes in lattice parameters are insufficient to stabilize a nonzero spin state, additional heteroepitaxial symmetry constraints---in particular the suppression of octahedral rotations---stabilize a ferromagnetic intermediate-spin state. By comparing with experimental data for the bulk material, we calculate an upper bound on the Hubbard $U$ value, and describe the role that the on-site Coulomb interaction plays in determining the spin-state configuration.