Doped holes and Mn valence in manganites: a polarized soft x-ray absorption study ofLaMnO3 and quasi-2D manganite systems

Abstract

The question of Mn valence and symmetry and population of doped holes inLa1.2Sr1.65Ca0.15Mn2O7 and LaSr2Mn2O7 bilayer single crystals has been studied with polarized soft x-ray absorption spectroscopy.The observed changes in the O K and Mn L spectra with polarization provide a strongindication for the existence of a competition between the charge dynamics and the latticedistortion that leads to transfer of some of the holes doped in the out-of-plane(3z2−r2) states tothe in-plane (x2−y2) states. The changes observed in these with doping are shown not due to a decrease in the electron populationin the dx2−y2 states but caused by an increase in density of holes in thedz2−x2 and dz2−y2 states, and the electrons predominantly occupy the corresponding orthogonal states, i.e.,d3x2−r2 and d3y2−r2. No evidence is found for the existence of a formalMn4+ valence state in these systems.