Control of octahedral rotations in (LaNiO3)n/(SrMnO3)msuperlattices

Abstract

Oxygen octahedral rotations have been measured in short-period (LaNiO${}_3$)${}_n$/(SrMnO${}_3$)${}_m$ superlattices using synchrotron diffraction. The in-plane and out-of-plane bond angles and lengths are found to systematically vary with superlattice composition. Rotations are suppressed in structures with $m>n$, producing a nearly unrotated form of LaNiO${}_3$. Large rotations are present in structures with $m<n$, leading to reduced bond angles in SrMnO${}_3$. The metal-oxygen-metal bond lengths decrease as rotations are reduced, in contrast to behavior previously observed in strained, single-layer films. This result demonstrates that superlattice structures can be used to stabilize nonequilibrium octahedral behavior in a manner distinct from epitaxial strain, providing a novel means to engineer the electronic and ferroic properties of oxide heterostructures.