Valence electronic structure of Mn in undoped and doped lanthanum manganites from relative K x-ray intensity studies

Abstract

Relative $K$ x-ray intensities of $Mn$ in $Mn$, $Mn{O}_2$, $LaMn{O}_3$ and $L{a}_{0.7}{B}_{0.3}Mn{O}_3$ ($B$ = $Ca$, $Sr$, and $Ce$) systems have been measured following excitation by 59.54 keV $\gamma$-rays from a 200 mCi ${}^{241}$Am point-source. The measured results for the compounds deviate significantly from the results of pure $Mn$. Comparison of the experimental data with the multiconfiguration Dirac-Fock (MCDF) effective atomic model calculations indicates reasonable agreement with the predictions of ionic model for the doped {manganites except} that the electron doped $L{a}_{0.7}C{e}_{0.3}Mn{O}_3$ and hole doped $L{a}_{0.7}C{a}_{0.3}Mn{O}_3$ compounds show some small deviations. The results of $Mn{O}_2$ and $LaMn{O}_3$ deviate considerably from the predictions of the ionic model. Our measured $K\beta /K\alpha$ ratio of $Mn$ in $L{a}_{0.7}C{a}_{0.3}Mn{O}_3$ cannot be explained as a linear superposition of $K\beta /K\alpha$ ratios of $Mn$ for the end members which is in contrast to the recent proposal by Tyson et al. from their $Mn$ $K\beta$ spectra.

14 pages, 4 figures. to appear in NIM-B.Please send an e-mail for figures