Scanning tunneling spectroscopy ͑STS͒ experiments were performed on the ͑001͒ and ͑111͒ surfaces of single crystalline magnetite. Room temperature spectra exhibit a ϳ0.2 eV gap around E f . The importance of perfect surface order to the existence of this gap is illustrated. STS is also carried out on the ͑111͒ surface, at 140 and 95 K, just above and below the Verwey transition temperature ͑T V ϳ 120 K͒, respectively. It is confirmed that above T V a ϳ0.2 eV gap exists in the surface density of states ͑DOS͒ around E f . Furthermore, broad bands are resolved on both sides of E f , with peaks centered on ϳ + 0.5 eV and ϳ−0.45 eV. Below T V it is shown that the value of the gap in the surface DOS remains similar, however, the peaks resolved in the conduction and valence bands shift markedly away from E f . The similarity of the gap value before and after the transition points away from an ionic charge ordering occurring at the magnetite surface below T V . However, the shifting of the bands points to a certain degree of electronic ordering or charge disproportionation playing an integral part in the Verwey transition, at the magnetite surface.

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STM tips made from antiferromagnetic MnNi have been used to investigate the atomic structure of the (001) and (111) surfaces of Fe 3 O 4 . The clean (001) surface displays a (√2 × √2)R45° superlattice, which is attributed to charge-ordering on the surface, where Fe 2+ -Fe 2+ and Fe 3+ -Fe 3+ dimers can be discriminated. The oxygenterminated (111) surface is characterized by an hexagonal superlattice with a periodicity of 42 Å. Oxygen vacancies are observed in atomically resolved images of this superlattice. In the presence of an external magnetic field of 60 mT, a significant change in the atomic corrugation in the topmost oxygen layer around each of these defects is observed. The results on both (001) and (111) surfaces are discussed in terms of possible spin polarized effects.