Temperature dependent changes of the Mn 3d and 4p bands near T${}_c$ in Colossal Magnetoresistance systems: a XANES study of La${}_{1-x}$Ca${}_x$MnO${}_3$

Abstract

We report high-resolution X-ray Absorption Near Edge Structure (XANES) measurements at the Mn K-edge as a function of temperature, for La${}_{1-x}$Ca${}_x$MnO${}_3$ samples, with a focus mainly on the pre-edge region. Small peaks labeled A${}_1$-A${}_3$ are observed which corresponds to 1s-3d dipole-transitions, made weakly allowed via a hybridization of Mn 4p states with Mn 3d states on {\it neighboring} atoms. Adjusting the parameters in an LSDA calculation to approximately match the experimental A${}_1$-A${}_2$ splitting yields U = 4 eV and J${}_H$ = 0.7 eV. For colossal magnetoresistance samples, A${}_1$ decreases with T while A${}_2$ increases with T below T${}_c$, which shows that the 3d bands change significant as T moves through T${}_c$. There are also small changes in the shape of the main edge (1s-4p transitions).

6 pages, 5 figures