Effect of strain on the stability and electronic properties of ferrimagnetic Fe${}_{2-x}$Ti${}_x$O${}_3$ heterostructures from correlated band theory

Based on density functional theory (DFT) calculations including an on-site Hubbard $U$ term we investigate the effect of substrate-induced strain on the properties of ferrimagnetic Fe${}_2$O${}_3$-FeTiO${}_3$ solid solutions and heterostructures. While the charge compensation mechanism through formation of a mixed \fetw, \feth-contact layer is unaffected, strain can be used to tune the electronic properties of the system, e.g. by changing the position of impurity levels in the band gap. Straining hematite/ilmenite films at the lateral parameters of Al${}_2$O${}_3$(0001), commonly used as a substrate, is found to be energetically unfavorable as compared to films on Fe${}_2$O${}_3$(0001) or FeTiO${}_3$(0001)-substrates.