Magnetic coupling parameters at an oxide-oxide interface from first principles:Fe2O3-FeTiO3

Abstract

Charge mismatch at the interface between canted antiferromagnetic hematite $(\ensuremath{\alpha}{\text{-Fe}}_{2}{\text{O}}_{3})$ and antiferromagnetic ilmenite $({\text{FeTiO}}_{3})$ is accommodated by the formation of mixed ${\text{Fe}}^{2+}$ and ${\text{Fe}}^{3+}$ contact layers, leading to uncompensated magnetic moments in the system. To derive the magnetic exchange interaction parameters of the end members and interface, we map total-energy differences of collinear spin arrangements obtained from density-functional theory calculations to a Heisenberg Hamiltonian using the least-squares method. Parameters for the end members, hematite $({J}_{m}^{3+,3+})$ and ilmenite $({J}_{m}^{2+,2+})$ are in good agreement with the values obtained from inelastic neutron-scattering data. The magnetic interaction parameters between ${\text{Fe}}^{2+}$ and ${\text{Fe}}^{3+}$ $({J}_{m}^{2+,3+})$ in the contact layer show a strong antiferromagnetic coupling to the adjacent hematite layers and thus explain the ferrimagnetism in the system.