Surface Electronic Structure of Post-Annealed La_0.67Sr_0.33MnO₃ Epitaxial Thin Films on SrTiO₃(100)

Abstract

The surface electronic structure of as-deposited and post-annealed La0.67Sr0.33MnO3 (LSMO) thin films on SrTiO3 (100) substrates has been studied by soft-X-ray spectroscopy. The crystal lattice reduces by post-annealing in air at 1100 C. The electrical resistivity also decreases by the postannealing. These thin films has the mixed valence states of Mn 3+ and Mn 4+ . The valence band near the Fermi level (EF) consists of the eg  and t2g  states of Mn 3d. The density of state at EF is higher in the post-annealed LSMO thin film.These results directly indicate that the change of the Mn valence state is closely related to the electrical resistivity and Mn 3d electron number of LSMO thin film at the surface state.