  Geometrical frustration of the Fe ions in LuFe2O4 leads to intricate charge
and magnetic order and a strong magnetoelectric coupling. Using resonant x-ray
diffraction at the Fe K edge, the anomalous scattering factors of both Fe sites
are deduced from the (h/3 k/3 l/2) reflections. The chemical shift between the
two types of Fe ions equals 4.0(1) eV corresponding to full charge separation
into Fe2+ and Fe3+. Polarization and azimuthal angle dependence of the
superlattice reflections demonstrates the absence of anisotropic scattering
revealing random orientations of the Fe2+ orbitals characteristic of an orbital
glass state.
