Structural effects on the spin-state transition in epitaxially strained LaCoO$_3$ films

TL;DR

This study uses density functional theory to explore how epitaxial strain and symmetry constraints influence the spin state and magnetic properties of LaCoO3 films, highlighting the importance of octahedral rotations and Coulomb interactions.

Contribution

It demonstrates that symmetry constraints, especially suppression of octahedral rotations, are crucial for stabilizing ferromagnetic intermediate-spin states in strained LaCoO3 films.

Findings

Strain alone does not stabilize a non-zero spin state.

Suppression of octahedral rotations stabilizes ferromagnetic intermediate-spin state.

The Hubbard U value influences the spin-state stability.

Abstract

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 non-zero 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.