Temperature-Dependent X-Ray Absorption Spectroscopy of Colossal Magnetoresistive Perovskites

The temperature dependence of the O $K$-edge pre-edge structure in the x-ray absorption spectra of the perovskites ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{A}}_{x}\mathrm{Mn}{\mathrm{O}}_{3}$ ($A=\mathrm{Ca},\mathrm{Sr}$; $x=0.3,0.4$) reveals a correlation between the disappearance of the splitting in the pre-edge region and the presence of Jahn-Teller distortions. The different magnitudes of the distortions for different compounds are proposed to explain some dissimilarities in the line shapes of the spectra taken above the Curie temperature.