Doping effect on the charge ordering in LuFe2O4

Matsuo, Yoji*; Shinohara, Satoshi*; Mori, Shigeo*; Horibe, Yoichi*; Yoshii, Kenji  ; Ikeda, Naoshi*

Change of the charge ordered (CO) structure by substituting Cu for Fe in LuFeO was investigated by means of the transmission electron microscopy. The CO structure in LuFeO is characterized by the modulated structure with the wave vector of q=1/3[1 -1 3/2] and the average size of the CO domains can be estimated to be about 10-20nm. On the contrary, the Cu substitution destroyed the CO structure drastically and induced characteristic local lattice distortion, which gives rise to characteristic diffuse scattering in the reciprocal space. High-resolution lattice images revealed that there exist nano-scale clusters, which are characterized as the short-range ordering of the Cu and Fe ions on the triangular lattice. In addition, the magnetic measurement revealed that LuFeCuO exhibits an antiferromagnetic transition around 50K, which is lower than the Neel temperature of 250K in LuFeO.