Temperature dependent changes of the Mn 3d and 4p bands near T- c in colossal magnetoresistance systems: XANES study of La1- xCaxMnO3: XANES study of La1-xCaxMnO3

We report high-resolution x-ray-absorption near-edge structure measurements at the Mn K edge as a function of temperature, for La1−xCaxMnO3 samples, with a focus mainly on the pre-edge region. Small peaks labeled A1–A3 are observed which correspond to 1s−3d dipole transitions, made weakly allowed via a hybridization of Mn 4p states with Mn 3d states on neighboring atoms. Adjusting the parameters in a local spin-density approximation calculation to approximately match the experimental A1−A2 splitting yields U=4 eV and JH=0.7 eV. For colossal magnetoresistance samples, A1 decreases with T while A2 increases with T below Tc, which shows that the 3d bands change significantly as T moves through Tc. There are also small changes in the shape of the main edge (1s−4p transitions).