Local lattice distortion caused by short-range charge ordering in transition metal oxides

遷移金属酸化物における電荷の短距離秩序が引き起こす局所構造歪み

樹神 克明   ; 井川 直樹   ; 社本 真一  ; 池田 一貴*; 大下 英敏*; 金子 直勝*; 大友 季哉*; 鈴谷 賢太郎; 星川 晃範*; 石垣 徹*

Kodama, Katsuaki; Igawa, Naoki; Shamoto, Shinichi; Ikeda, Kazutaka*; Oshita, Hidetoshi*; Kaneko, Naokatsu*; Otomo, Toshiya*; Suzuya, Kentaro; Hoshikawa, Akinori*; Ishigaki, Toru*

Cubic spinel compound LiMnO with the mixed valence of Mn has non-metallic conductivity. The local structure determined by the PDF analysis has an orthorhombic lattice distortion and includes inequivalent Mn and Mn sites. YBaCoO also exhibits non-metallic conductivity although the Co has the mixed valence of +2.5 above 220 K which corresponds with charge ordering temperature. The PDF obtained at 450 K is not reproduced by the PDF calculated for the averaged structure and can be reproduced by the PDF calculated for the structure model corresponding to the charge ordering state. These results suggest that the valence electrons are localized with short-range periodicity, resulting in the non-metallic conductivities in these materials.