First-principles LSDF study of weak ferromagnetism in Fe2O3

We report results of calculations that explain in the itinerant electron picture weak ferromagnetism in hematite, alpha-Fe2O3. We use the local approximation to spin-density functional theory and the ASW method incorporating spin-orbit coupling (SOC) and non-collinear moment arrangements. By a detailed symmetry analysis we show how the relativistic effect of SOC and the particular crystal symmetry of alpha-Fe2O3 cooperate to lead to a non-collinear magnetic structure and thus to weak ferromagnetism.