We report resonant x-ray scattering studies of charge and orbital order in Pr_{1-x}Ca_{x}MnO_3 with x=0.4 and 0.5. Below the ordering temperature, T_O=245 K, the charge and orbital order intensities follow the same temperature dependence, including an increase at the antiferromagnetic ordering temperature, T_N. High resolution measurements reveal, however, that long range orbital order is never achieved. Rather, an orbital domain state is formed. Above T_O, the charge order fluctuations are more highly correlated than the orbital fluctuations. Similar phenomenology is observed in a magnetic field. We conclude that the charge order drives the orbital order at the transition.
@article{arxiv.cond-mat/9905285,
title = {Interplay between charge, orbital and magnetic order in Pr_{1-x}Ca_xMnO_3},
author = {M. v. Zimmermann and J. P. Hill and Doon Gibbs and M. Blume and D. Casa and B. Keimer and Y. Murakami and Y. Tomioka and Y. Tokura},
journal= {arXiv preprint arXiv:cond-mat/9905285},
year = {2009}
}