Evidence for Mn 2+ ions at surfaces of La 0. 7Sr 0.3MnO 3 thin films

M. P. De Jong*, I. Bergenti, V. A. Dediu, M. Fahlman, M. Marsi, C. Taliani

*Corresponding author for this work

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Abstract

We present a detailed investigation of the valence of manganese sites at the surface of colossal magnetoresistance La 0.7Sr 0.3MnO 3 (LSMO) thin films by x-ray absorption spectroscopy (XAS). The XAS Mn L-edge spectra of epitaxial LSMO films usually show a peak or shoulder at 640 eV. Differences in the intensity of this feature are commonly attributed to slight changes in the Mn 3+/Mn 4+ ratio or the crystal field strength. By comparison of different XAS spectra of LSMO thin films with the known multiplet structure of Mn 2+ in a cubic crystal field, we assign this 640-eV feature to Mn 2+ ions. XAS with increased surface sensitivity, combined with photon energy-dependent photoelectron spectroscopy measurements of the Mn(3s) exchange splitting, show that the Mn 2+ species are mainly located at the surface. The Mn 2+ scenario indicates significant modification of the LSMO surface with respect to the bulk properties that should be taken into account in all the charge and spin tunneling and injection experiments.

Original languageEnglish
Article number014434
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume71
Issue number1
DOIs
Publication statusPublished - Jan 2005
Externally publishedYes

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