NMR studies in quasi-1D pressure-induced superconductor β-Ag0.33V2O5

A series of vanadium bronzes, beta-A(0.33)V(2)O(5) (A = Li; Na; Ag,...) is known to exhibit metal-insulator transition (MIT) accompanied with successive charge-spin orderings at ambient pressure. Recently, the series of compounds has been paid much attention since superconductivity was discovered under high pressure above 7 GPa. We have performed nuclear magnetic resonance (NMR) on V-51 nuclei at ambient pressure and observed three kinds of vanadium signals above 30 K. We found that these signals originate from three crystallographically inequivalent vanadium sites. The quadrupole coupling constant upsilon(Q) is estimated from the NMR spectra, which gives a measure of the charge density. Our results show that all vanadium sites have charge density even at low temperatures below the MIT temperature. (c) 2006 Elsevier B.V. All rights reserved.