Band theory for electronic and magnetic properties of alpha-Fe2O3

We report results of calculations that explain in the itinerant-electron picture magnetic and electronic properties of haematite, alpha-Fe2O3. For this we use the local approximation to spin-density functional theory and the ASW method incorporating spin-orbit coupling and noncollinear moment arrangements. The insulating character of the compound is obtained correctly and features in the density of states connected with Fe-O hybridization correlate well with experimental features seen in direct and inverse photoemission intensities. The total energy correctly predicts the experimentally observed magnetic order of the ground state, and, using total energies of different magnetic configurations, we can give a rough estimate of the Neel temperature. We also obtain a state showing weak ferromagnetism. The rate of change is calculated for the decrease of the insulating gap when an external magnetic field is applied.