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.

• Received 22 December 2008

DOI:https://doi.org/10.1103/PhysRevB.79.054409