Evidence for orbital ordering in LaCoO3

TL;DR

This paper provides structural evidence for orbital ordering in LaCoO3, showing a temperature-dependent Jahn-Teller distortion linked to spin state transitions of Co3+ ions.

Contribution

It presents direct diffraction evidence of orbital ordering and Jahn-Teller distortions in LaCoO3 associated with spin state changes.

Findings

Monoclinic distortion observed in LaCoO3 at low and intermediate spins

Jahn-Teller distortion increases with temperature

Evidence of thermally activated spin state transition

Abstract

We present powder and single crystal X-ray diffraction data as evidence for a monoclinic distortion in the low spin (S=0) and intermediate spin state (S=1) of LaCoO3. The alternation of short and long bonds in the ab plane indicates the presence of eg orbital ordering induced by a cooperative Jahn-Teller distortion. We observe an increase of the Jahn-Teller distortion with temperature in agreement with a thermally activated behavior of the Co3+ ions from a low-spin ground state to an intermediate-spin excited state.