Interface magnetism in Fe2O3/FeTiO3 heterostructures

To resolve the microscopic origin of magnetism in the Fe2O3/FeTiO3 system, we have performed density functional theory calculations that take into account on-site Coulomb repulsion. By systematically varying the concentration, distribution, and charge state of Ti in a hematite host, we compile a phase diagram of the stability with respect to the end members and find a clear preference to form layered arrangements as opposed to solid solutions. The charge mismatch at the interface is accommodated through Ti4+ and a disproportionation in the Fe contact layer into Fe2+, Fe3+, leading to uncompensated moments in the contact layer and giving first theoretical evidence for the lamellar magnetism hypothesis. This interface magnetism is associated with impurity levels in the band gap, showing a half-metallic behavior and making Fe2O3/FeTiO3-heterostructures prospective materials for spintronics applications.