Energetic stability and magnetic coupling in (Cr1-xFex)2O3: Evidence for a ferrimagnetic ilmenite-type superlattice from first principles

Based on density functional theory (DFT) calculations with a Hubbard U-term, we explore the possibility to design an artificial ferrimagnet FeCrO3 of ilmenite type out of the two antiferromagnets alpha-Fe2O3 and alpha-Cr2O3. By varying the concentration of Fe in alpha-Cr2O3, we provide a phase diagram of the relative stability of different chemical and magnetic arrangements with respect to the end members. At 50% Fe-doped alpha-Cr2O3, the ilmenite-like structure with alternating Fe and Cr layers and antiparallel magnetic moments competes energetically with a phase-separated structure containing a mixed Fe-Cr interface layer. The magnetic interaction parameters between Fe(3d(5)) and Cr(3d(3)) ions in the digital ferrimagnetic heterostructure, extracted by mapping the DFT total energies to a Heisenberg Hamiltonian, indicate a hematite-like magnetic order with parallel intralayer and antiparallel interlayer alignment.