Determination of the Lowest Unoccupied Orbital in the Layered Perovskite LaSrMnO4Using Polarized Oxygen K Edge Absorption Spectroscopy

Abstract

Using polarized oxygen K edge spectroscopy, the first unoccupied orbital of LaSrMnO 4 was investigated. The lowest unoccupied orbital is of minority spin d x z , d y z character instead of the majority spin d x 2 - y 2 character. The d x 2 - y 2 orbital would be expected based on Hund's rule and the strong exchange interaction of the one-electron addition d 5 system. The explanation is a strong ligand field splitting caused by the strong local site distortion of the Mn site which raises the energy of the majority spin d x 2 - y 2 orbital and lowers the energy of the d x z , d y z orbitals. At the same time the two-electron integrals, which are responsible for the exchange interaction, are screened because of covalency.