Determination of local distortions in the charge ordered and CMR La1-xCaxMnO3 manganites

We have studied charge ordered La0.5Ca0.5MnO3 and colossal magnetoresistive La0.75Ca0.25MnO3 system by Mn K-edge EXAFS to explore temperature dependent local displacements in the MnO6 octahedra. We provide a clear evidence for large octahedral distortions (Q3-type), coexisting with the small distortions (Q2-type) in the commensurate charge ordered phase at low temperature. Small Jahn-Teller (JT) distortions persist even at high temperature in the charge disordered phase indicating short-range charge correlations in the macroscopically disordered phase