CHARGE ORDERING OF LUFE2O4 OBSERVED BY AN ANOMALOUS X-RAY DISPERSION

We observed a superlattice reflection for triangular layered oxide LuF e2O4 by using anomalous X-ray dispersion with synchrotron radiation so urce. We found that superlattice spot (1/3, 1/3, 4.5) shows a large in tensity variation upon a slight change of incident X-ray energy (wave length) from 7.114 keV (1.7437 Angstrom) to 7.1448 keV (1.7353 Angstro m) across the Fe absorption edge. This phenomenon is explained by supe rlattice structure of Fe2+ and Fe3+ on triangular lattice. The existen ce of the superlattice structure due to the charge ordering of iron io ns on triangular lattice indicates that LuFe2O4 possesses local sponta neous polarization.