Using first-principles density functional theory, we have modeled the atomic, electronic and magnetic structure of epitaxial interfaces between alpha-hematite and alpha-chromia (corundum structure) in the hexagonal (0001) basal plane. Our model was a superlattice with a period of about 27.5 Å, corresponding to the shortest-period superlattice considered in a recent series of experiments [Chambers et al., Phys. Rev. B 61, 13223 (2000)]. Two different epitaxial interface structures were studied: $\mathrm{}\left(i\right)\mathrm{}$ an oxygen plane separating an Fe double layer from a Cr double layer or $\mathrm{}\left(\mathrm{ii}\right)\mathrm{}$ a metal double layer split between Fe and Cr. We found that these two structures are close in total energy but have distinct spin structure and different valence band offsets [chromia above hematite by 0.4 and 0.6 eV for $\mathrm{}\left(i\right)\mathrm{}$ and $\mathrm{}\left(\mathrm{ii}\right),$ respectively], possibly explaining the experimental noncommutative band offset seen in this system $(0.3\mathrm{}\pm 0.1\mathrm{eV}$ for hematite grown atop chromia, and $0.7\pm 0.1\mathrm{eV}$ for the reverse).

• Received 1 November 2003

DOI:https://doi.org/10.1103/PhysRevB.69.205106