Structural relations between two ground states of the axial next nearest neighbor Ising compound Na V2 O5, C1/4 and C0 phases below and above the transition pressure PC =1 GPa, were investigated by x-ray diffraction and scattering techniques. The structure of the C0 phase is well explained by the A (A′) pattern, which is one of four layers (AA A′ A′) of the C1/4 phase, however, the amount of the atomic shifts under the conditions 1.6 GPa and 6 K is 27% that under ambient pressure. On the other hand, resonant x-ray scattering showed that the charges are disproportionated under high pressure. Based on these facts, it was concluded that charge disproportionation corresponds to the Ising variable in Na V2 O5, where the atomic shifts are regarded as linearly coupled to the Ising spins. These results lead to the hypothesis that the competitive interactions between the Ising spins may result from the Ising spin-phonon coupling.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Sep 26 2007|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics