Eur. Phys. J. B 51, 315-319 (2006)
https://doi.org/10.1140/epjb/e2006-00228-4

O1s and Mn2p NEXAFS on single-layered La_1-xSr_1+xMnO₄: crystal field effect versus orbital coupling mechanism

¹ Institut für Kristallographie, Jägerstraße 17-19, RWTH Aachen, 52066 Aachen, Germany
² Institute for Solid State Research, P.O. Box 270116, IFW Dresden, 01171 Dresden, Germany
³ Naval Research Laboratory, Code 6345, Washington, DC, 20375, USA
⁴ Department of Physics, Montana State University, Bozeman, MT, 59717-3840, USA
⁵ Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76021 Karlsruhe, Germany

Corresponding author: ^a merz@xtal.rwth-aachen.de

Received: 20 December 2005
Revised: 14 March 2006
Published online: 13 June 2006

Abstract

O1s and Mn2p near-edge X-ray absorption spectroscopy on La_1-xSr_1+xMnO₄ (0 ≤x ≤0.5) single crystals shows that Sr doping does not only provide holes to the system but also induces a continuous transfer of electrons from out-of-plane d_3z2-r2 to in-plane d_3x2-r2/d_3y2-r2 orbitals. Furthermore, a non-vanishing electron occupation of in-plane d_x2-y2 and out-of-plane d_3z2-r2 orbitals is observed up to relatively high doping contents. These findings demonstrate that the energy difference between all these orbital types has to be very small and manifest that the orbital degree of freedom is determined not just by crystal field effects but also by orbital coupling. Moreover, the doping-dependent transfer of spectral weight observed in the current data identifies La_1-xSr_1+xMnO₄ as a charge-transfer insulator.