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.
Digital Commons Citation
Trappen, Robbyn; Garcia- Castro, A. C.; Tra, VU Thanh; Huang, Chih-Yeh; Ibarra-Hernandez, Wilfredo; Fitch, James; Singh, Sobhit; Zhou, Jingling; Cabrera, Guerau; Chu, Ying-Hao; LeBeau, James M.; Romero, Aldo H.; and Holcomb, Mikel B., "Electrostatic potential and valence modulation in La0.7Sr0.3MnO3 thin films" (2018). Faculty & Staff Scholarship. 1359.
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). https://doi.org/10.1038/s41598-018-32701-x