Evolution of charge order through the magnetic phase transition of LuFe2O4

The charge order in multiferroic LuFe2O4 has been investigated with resonant x-ray diffraction at the Fe K edge in the combined charge ordered and magnetic phase. The energy dependence of the charge order reflection (1/3 1/3 7/2) has been analyzed in detail to investigate the charge disproportionation between the iron sites as a function of temperature. It is found that the charge disproportionation is constant within 0.02e across the Neel temperature T-N. The charge order reflection exhibits a decrease in intensity with increasing temperature which is attributed to an increase in the probability of electron hopping. We confirm the increase in polarization at T-N is not of static origin but rather dynamic. Our observations are consistent with antiferromagnetically aligned magnetic moments inhibiting the double exchange mechanism and reducing the probability of electrons hopping between Fe2+ and Fe3+ in the magnetic phase.