Geometric local structure at the Mn site in charge‐ordered mixed valence manganites

An extensive study of Mn K‐edge absorption spectroscopy has been carried out in La 1‐x Ca x MnO 3 and Tb 1‐x Ca x MnO 3 (x=0, 0.33, 0.5, 0.67, 1) series as a function of temperature. The EXAFS analysis for the charge ordering compounds (x ≥ 0.5) shows the presence of a static distortion of the MnO6 octahedron in the whole temperature range. However, this local distortion is lower than the distortion found for Jahn‐Teller compounds. Magnetoresistive compounds (x=0.33) show a regular octahedron in the low temperature metallic phase. Instead, no changes are found for the first coordination shell (Mn‐O) across the charge ordering transition while Mn‐Mn distribution shows minor variations with the temperature. The structural analysis of the second coordination shell suggests that the Mn‐O‐Mn angle is the most relevant parameter to describe the electric and magnetic behaviour of these compounds.