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.
@article{arxiv.cond-mat/0304651,
title = {Evidence for orbital ordering in LaCoO3},
author = {G. Maris and Y. Ren and V. Volotchaev and C. Zobel and T. Lorenz and T. T. M. Palstra},
journal= {arXiv preprint arXiv:cond-mat/0304651},
year = {2009}
}