Local distortion in LaMnO3 across the Jahn-Teller transition

We report on an X-ray absorption study on the temperature dependence of the local organisation around Mn3+ in a high-quality LaMnO3.00 ceramics. The structural transition is clearly evidenced by modifications on the EXAFS spectra across the Jahn-Teller transition. These modifications are associated with alterations in the MnO6 polyhedral arrangement. There is no experimental evidence of any reduction of the static disorder in the coordination shell around the Mn3+ at high temperature. This result supports the hypothesis that the Jahn-Teller transition would correspond to a change from a static and cooperative distortion to a dynamic one, without remotion of the local distortions present in the MnO6 below the JT temperature. (C) 2001 Elsevier Science B.V. All rights reserved.