•Michael Merz¹, P. Reutler², B. Büchner², Y. U. Idzerda³, S. Tokumitsu⁴, N. Nücker⁴ und S. Schuppler^4
1Institut für Kristallographie, RWTH Aachen
²Institut für Festkörper- und Werkstoffforschung, Dresden
³Naval Research Laboratory, Washington
⁴Forschungszentrum Karlsruhe, Institut für Festkörperphysik

Manganites exhibit a manifold of highly interesting magnetic and electronic phases, with charge- and orbital-ordered states being at the center of interest. Especially single-layered La_1-xSr_1+xMnO₄ is a prototypical example for such ordering effects. For this compound a ferro-orbital ordering of |3z2-r2 > states is expected from the strong crystal field, yet anti-ferro type orbital coupling might lead to an admixture of |x2-y2 > states.

Using polarization-dependent O1s and Mn2p near-edge x-ray absorption spectroscopy on untwinned La_1-xSr_1+xMnO₄ single crystals (0 £ x £ 0.5), the doping- and temperature-dependent occupancies of the O2p and Mn3d orbitals were studied. According to the spectra, Sr doping not only provides holes to the system but also induces a continuous transfer of electrons from out-of-plane |3z2-r2 > to in-plane |3x2-r2 > and |3y2-r2 > states. The data clearly demonstrate that electrons reside for all doping levels on mixed a|3z2-r2 > + b|x2-y2 > states, i. e., antiferro-coupled canted orbitals where a and b strongly depend on the Sr content.