We have used density-functional theory with the gradient corrected exchange-correlation functional PW91 to study the effect of an interfactant layer, where Fe and Cr are replaced by a different metal, on electronic and magnetic properties of an epitaxial interface between a- Fe2 O3 and a- Cr2 O3 in the hexagonal (0001) basal plane. We studied a monolayer of M2 O3 (M=Al,Ga,Sc,Ti,Ni) sandwiched with five layers of chromia and five layers of hematite through epitaxial interfaces of two types, termed "oxygen divided" or "split metal." We found that both the electronic and magnetic properties of the superlattice are modified by the interfactant monolayer. For the split-metal interface, which is favored through the growth pattern of chromia and hematite, the valence-band offset can be changed from 0.62 eV (no interfactant) up to 0.90 eV with the Sc2 O3 interfactant, and down to -0.51 eV (i.e., the a- Fe2 O3 a- Cr2 O3 heterojunction changes from type II to type I) with the Ti2 O3 interfactant, due to a massive interfacial charge transfer. The band gap of the system as a whole remains open for the interfactant monolayers based on Al, Ga, and Sc, but it closes for Ti. For Ni, the split-metal interface has a negative band offset and a small band gap. Thus, nanoscale engineering through layer-by-layer growth will strongly affect the macroscopic properties of this system. © 2007 The American Physical Society.
|Journal||Physical Review B: Condensed Matter and Materials Physics|
|Publication status||Published - 15 May 2007|