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Eberly College of Arts and Sciences


Physics and Astronomy


The Mn valence in thin film La0.7Sr0.3MnO3 was studied as a function of film thickness in the range of 1–16 unit cells with a combination of non-destructive bulk and surface sensitive X-ray absorption spectroscopy techniques. Using a layer-by-layer valence model, it was found that while the bulk averaged valence hovers around its expected value of 3.3, a significant deviation occurs within several unit cells of the surface and interface. These results were supported by first principles calculations. The surface valence increases to up to Mn3.7+, whereas the interface valence reduces down to Mn2.5+. The change in valence from the expected bulk value is consistent with charge redistribution due to the polar discontinuity at the film-substrate interface. The comparison with theory employed here illustrates how this layer-by-layer valence evolves with film thickness and allows for a deeper understanding of the microscopic mechanisms at play in this effect. These results offer insight on how the two-dimensional electron gas is created in thin film oxide alloys and how the magnetic ordering is reduced with dimensionality.

Source Citation

Trappen, R., Garcia-Castro, A. C., Tra, V. T., Huang, C.-Y., Ibarra-Hernandez, W., Fitch, J., … Holcomb, M. B. (2018). Electrostatic potential and valence modulation in La0.7Sr0.3MnO3 thin films. Scientific Reports, 8(1).


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