Mixed valences in nanometric ferrites investigated by resonant powder diffraction

Abstract

The dependence of the absorption-edge position on ion valence in resonant scattering can be used to analyse the ionic composition of complex oxides. As the diffraction spectra are more sensitive to f^{\,\prime} than to f^{\,\prime\prime}, the shift in f^{\,\prime} associated with the valence can be used to refine the cation distribution. Below the absorption edge the shape of f^{\,\prime} is quite insensitive to other site parameters. High-angle data are important to reach significant variation of the diffraction lines. The feasibility of this method for powder materials was tested using a nanometric powder of magnetite, Fe3O4. More complex ferrites were then investigated and the results compared with neutron diffraction experiments.