Structural effects on the spin-state transition in epitaxially strained LaCoO3 films

Using density-functional theory within the LSDA+U method, we investigate the effect of strain on the spin state and magnetic ordering in perovskite lanthanum cobaltite, LaCoO3. 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.