Electronic structure and hyperfine fields in non-stoichiometric magnetite above the Verwey transition

The NMR spectra of Fe-57 nuclei were measured below and above the Verwey transition temperature TV in single crystal samples of Fe3(1-delta)O4 (0 <=delta <= 0.009). The measured crystals were grown from the melt using the cold crucible technique. In a cubic phase above TV the satellite structure induced by vacancies in the octahedral sublattice is clearly resolved. The satellite lines originate from those iron nuclei in the tetrahedral sublattice that are nearest to the vacancy. Temperature dependence of satellite lines indicates that the presence of vacancy leads to are distribution of the electrons in octahedral sublattice and the appearance of iron ions possessing appreciable orbital momentum. (C) 2009 Elsevier B.V. All rights reserved.