Local Lattice Distortion Caused by Short-Range Charge Ordering in Transition Metal Oxides

Abstract

We have performed local structural analysis by using the atomic pair distribution function (PDF) on LiMn 2 O 4 and YBaCo 2 O 5 which contain the single Mn and Co sites with the half-integer valences of +3.5 and +2.5, respectively, to reveal the local lattice distortion caused by the short-range charge ordering. The local structure of cubic spinel compound LiMn 2 O 4 at room temperature determined by the PDF analysis has an orthorhombic lattice distortion and includes inequivalent Mn sites with the valences of +3 and +4. The local structure of tetragonal phase of YBaCo 2 O 5 at 450 K has an orthorhombic lattice distortion including the inequivalent Co 2+ and Co 3+ sites. These results suggest that the valence electrons are localized at their transition metal sites only with short-range correlation, resulting in the non-metallic conductivity in these materials.