Examination Of Charge Order In Mixed Valence Oxide Lufe2o4 By Mossbauer Quadrupole Effect

The Fe2+/Fe3+ charge order (CO) in LuFe2O4 has been examined by Mossbauer quadrupole effect. The stoichiometric single crystal of LuFe2O4 was used to measure the paramagnetic spectrum at 282 K. The spectrum was analyzed by assuming the CO monoclinic structure (space group C2/m) with four inequivalent Fe sites, among which two are occupied by Fe3+ and other two are occupied by Fe2+. The obtained quadrupole parameters, quadrupole splitting QS and the intensity ratio of the two absorption lines I(+/- 3/2)/I(+/- 1/2), coincide well with those calculated from the crystal structure. On the other hand, the parameters obtained by assuming other two crystal structures previously proposed, the hexagonal structure with a single Fe site (R (3) over barm) and the monoclinic structure with a single Fe site (C2/m), are found to be inconsistent with the calculated ones. These results indicate that the CO monoclinic structure is most probable among the structural models proposed so far from the viewpoint of the Mossbauer quadrupole effect.