Atomic and electronic structure of the Fe₃O₄(111) / MgO(111) model polar oxide interface

Journal Article · Tue Nov 01 04:00:00 EST 2005 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.72.195401· OSTI ID:1152575

Lazarov, V.; Weinert, M.; Chambers, S.; Gajdardziska-Josifovska, M.

High-resolution transmission electron microscopy HRTEM and density functional calculations are used to study the effect of interface polarity on the atomic and electronic structure of the prototype Fe₃O₄(111) / MgO(111) polar oxide interface. We show that atomically abrupt interfaces exist between the MgO (111) substrate and magnetite (111) film in regions separated by Fe nanocrystals, and propose a solution for this oxide-oxide interface structure. Comparisons of experimental HRTEM images with calculated through-focus and through-thickness images for model interface structures suggest metal-oxygen-metal i.e., Mg—O—Fe interface bonding with octahedral ( B) coordination of the first Fe monolayer, rather than the combination of tetrahedral-octahedral-tetrahedral ABA stacking also found in Fe₃O₄. First-principles calculations for all the different models find metal-induced gap states in the interface oxygen layer. Consistent with the HRTEM results, the MgO—Fe₃O₄ interface stacking ···, 4Mg/4O/4Mg/4O/3Fe_B/4O/Fe_AFe_BFe_A, ···, is calculated to be the energetically most favorable, and effectively screening the MgO (111) substrate surface polarity. The data and calculations exclude mixing of Mg and Fe across the interface, in contrast to the commonly invoked mechanism of cation mixing at compound semiconductor polar interfaces.

• Research Organization: Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• OSTI ID: 1152575
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 19 Vol. 72; ISSN 1098-0121; ISSN PRBMDO
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English