The nature of the cooperative Jahn-Teller (JT) transition accompanied by orbital order-disorder in Nd1-xCaxMnO3 has been studied by high temperature (300 - 1200K) synchrotron and laboratory X-ray powder diffraction in the low doping region (0<x<0.1). For very low doping a large temperature range of phase coexistence associated with a first-order transition has been observed, resembling a martensitic transformation. The transition appears continuous because of a gradual evolution of the volume fractions of the phases over a broad temperature interval. The first-order nature of the transition and the phase coexistence is suppressed with increasing of doping.
@article{arxiv.0710.3723,
title = {Continuous first order orbital order-disorder transition in Nd1-xCaxMnO3},
author = {C. V. Colin and A. J. C. Buurma and M. v. Zimmermann and T. T. M. Palstra},
journal= {arXiv preprint arXiv:0710.3723},
year = {2009}
}