Hard x-ray probe to study doping-dependent electron redistribution and strong covalency in La1-xSr1+xMnO4

The doping dependence of the occupied 3d states at the Mn sites of La1-xSr1+xMnO4 (x=0, 0.3, and 0.5) was studied by means of nonresonant hard x-ray emission spectroscopy. For the single-crystalline samples, we observe a linear dichroism of the Mn K beta main lines (3p to 1s transitions) that is strongest for x=0 and decreases with increasing hole doping x. At the same time, the Mn K beta main lines of polycrystalline samples, i.e., the angular-integrated spectra, remain almost unchanged upon hole doping. The linear dichroism in the single crystals and the invariance of the K beta lines in polycrystals lead to the conclusion that hole doping causes a spatial redistribution of the 3d electrons without reducing the total charge and spin density at the manganese sites. This implies that the doped holes in La1-xSr1+xMnO4 must have a strong oxygen 2p character. Many-body cluster calculations are presented that support these findings.