Study of the electron structure of Mn, Sr, La, Ce, and Sm cations in Ln_{1 − x} Sr _x MnO₃ (Ln = La, Ce, Sm) manganites by the X-ray line shift method

Abstract

The X-RayK _α line shifts of all cations in Ln_{1 − x} Sr _x MnO₃ (Ln = La, Ce, Sm) manganites have been measured using crystal diffraction spectrometers. The Mn K _αline shifts have been found in the Sm_{1 − x} Sr _x MnO₃ system correspond to an increase in the valence from Mn³⁺ to Mn⁴⁺. In the Ce_{1 − x} Sr _x MnO₃ system, in addition to this, the valence of cerium have been found also increases to almost 4. It is shown that the dependence of the valence of manganese on the content of strontium does not correspond to a simple model of the local mixture of Mn³⁺ and Mn⁴⁺ ions, which is usually applied to these systems. It is also demonstrated that the bonds of Sr, La, and Sm in the manganites studied exhibit a significant covalent character. In cation-deficient Sm_{1 − y} Mn_{1 − z} O₃, an increase in the valence of Mn is found accompanied by a decrease in the covalence of Sm.