Structural relations between two ground states of Na V2 O5 under high pressure: A synchrotron x-ray diffraction study

Kenji Ohwada, Yasuhiko Fujii, Jiro Muraoka, Hironori Nakao, Youichi Murakami, Yukio Noda, Hiroyuki Ohsumi, Naoshi Ikeda, Takahisa Shobu, Masahiko Isobe, Yutaka Ueda

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Abstract

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.

Original languageEnglish
Article number094113
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume76
Issue number9
DOIs
Publication statusPublished - Sep 26 2007

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ASJC Scopus subject areas

  • Condensed Matter Physics

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