Charge Order Induced by Cation Order in δ-Ag2/3V2O5

Abstract

Several compounds of vanadium bronze have drawn much interest as a stage of various quantum phenomena. The δ-phase of vanadium bronze has been investigated, focusing on the phase transition in δ-Ag2/3V2O5 which shows characteristic supercooling effects. In this study, we reveal that the phase transition accompanied by jumps of magnetic susceptibility and resistivity is caused by the Ag ions ordering. Furthermore, we also reveal that the Ag ion ordering triggers the V4+/V5+ charge ordering. The phase transition in δ-Ag2/3V2O5 is a novel charge ordering phenomenon induced by the cation ordering. A model of the Ag ion ordering is proposed from X-ray diffraction and electron diffraction analyses. A V4+/V5+ charge ordering model is also proposed and the spin-gapped ground state is discussed on the basis of the charge ordering model.