X-ray resonant scattering in Fe3O4, MnFe2O4 and CoFe2O4 ferrites

X-ray resonant scattering experiments at (002) and (006) forbidden Bragg reflections were performed on Fe3O4, MnFe2O4 and CoFe2O4 single crystals. The intensity of these reflections in Fe3O4 shows three characteristic features as a function of energy. A pre-peak resonance related to dipolar-quadrupolar transitions coming from the tetrahedral Fe ions and a main resonance at the absorption edge and the energy-extended oscillating part ascribed to the anisotropy of the octahedral Fe ions. X-ray resonant scattering experiments on MnFe2O4 (normal spinel) and CoFe2O4 (inverse spinel) ferrites verify experimentally the origin of these resonances, the main peak is caused by the dipole transition of the octahedral site iron and the pre-edge peak is due to the dipole-quadrupole transition of the tetrahedral site iron, independently of the formal valency or chemical specie. These experimental results show that anisotropic tensor susceptibility (ATS) scattering cannot be simply considered as a direct proof of orbital ordering.