Nuclear Quadrupole Effect and Phase Transition in the Quasi‐One‐Dimensional Conductor β‐Na_0.33 V₂O₅

Abstract

The angular dependence of the main NNR resonance lines of the 61V nuclei in @-Nao.ssV20, is measured above and below the first-order structural phase transition temperature in the frequency range between 10 and 20 XHz. The nuclear quadruple interaction parameters of the broad resonance line are determined, and the principal axes of the electric field gradient tensor are found to coincide with those of the crystalline field around the vanadium atoms in site I.La dependance angulaire des lignes principales de resonance de 'IV nucleus dam P-Nao.33V20s a 6th mesure6 au dessus et au dessous de la temperature structurale de transition de phase de premier ordre, dans un eventail de frequence entre 10 et 20 MHz. Les parametres de I'interaction nucleaire quadrupolaire de la ligne de resonance ont BtB determine et les axes principaux du tenseur du gradient du champ electrique ont 6t6 trouvh pour coincides avec ceux du champ cristallin autour des atomes de vanadium en position I.

Electron density in the sodium vanadium oxide bronze β-Na x V2O5 at 9 K

“…The existence of the V 4+ ±V 4+ spin-singlet pairs (bipolarons) formed by strong electron±phonon coupling was suggested by Chakraverty et al (1978) in order to explain the high quasi-one-dimensional electrical conductivity. The existence of bipolarons was also supported by the anomalous temperature dependence of the 51 V Knight shift in the NMR spectra (Onoda et al, 1982), as well as by accurate EPR measurements of the g-shift and signal line-width angular dependence (Takahashi & Nagasawa, 1981). Thus, the anisotropy of the electrical conductivity can be explained by bipolarons travelling along the y axis while the conductivity in the other two perpendicular directions is due to a diffusive electron hopping motion (Onoda & Nagasawa, 1983).…”

Magnetic ordering in the mixed-valence compoundβ−Na0.33V2OВасильев1, Марченко2, Смирнов3 et al. 2001Phys. Rev. B390330View full textAdd to dashboardCite

“…The V 4+ ions are in a magnetic S = 1 2 state, while the V 5+ ions with S = 0 are nonmagnetic. Basing on interatomic distances 10 and on NMR measurements 11,12 it was concluded that in the high temperature phase T > T c the donated electrons are situated at the V1 sites, with one half of these sites being V 4+ . The recent NMR experiments on V-ions 13 confirm the charge ordering nature of the transition at T = T c and reveal that the number of inequivalent V positions below T c is increased.…”