Spectroscopy of La0.5Sr1.5MnO4 orbital ordering: a cluster many-body calculation

Abstract.Orbital ordering (OO) in La0.5Sr1.5MnO4 has been studied using soft X-ray resonant diffraction (SXRD) at the Mn L2,3 edges in combination with many-body cluster calculations. The SXRD intensity is modelled in second quantization using a small planar cluster consisting of a central active Mn site with first-neighbour shells comprising O and Mn sites. The effective Hamiltonian includes Slater-Koster parameters and charge transfer and electron correlation energies obtained from previous measurements on manganites. The energy dependence of the SXRD OO peak is calculated using the Jahn-Teller distortions of the oxygen octahedra and in-plane spin correlations as adjustable parameters. These contributions are clearly distinguished above the Néel temperature with a good spectroscopic agreement. The results also suggest a significant charge separation between the Mn sites.

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