Little volume change in orbital ordering transition in manganite thin films

We have investigated the structural feature of orbital-ordering manganite thin films fabricated on the perovskite (011) substrates by means of synchrotron x-ray diffraction technique. Like bulk manganites, these films show large jumps in lattice parameters at the orbital ordering transition temperature, which clearly show the transitions are first order. However, the magnitude of the volume change at the transition temperature for the films is much smaller than that for the orbital ordering transition in bulk manganite. This difference is understood by taking into account the stress from the substrate.