Charge-order-driven spin-peierls transition in alpha(')-NaxV2O5
We conclude from 23Na and 51V NMR measurements in alpha(')-NaxV2O5 (x = 0.996) (i) a charge-ordering transition starting at T</=37 K and preceding the lattice distortion and (ii) the formation of a spin gap Delta = 106 K at T(c) = 34.7 K. Above T(c), only a single Na site is observed in agreement with the Pmmn space group of this first 1/4-filled ladder system. Below T(c) = 34.7 K, this line evolves into eight distinct 23Na quadrupolar split lines, which evidences a lattice distortion with, at least, a doubling of the unit cell in the (a,b) plane. A model for this unique transition, implying both charge density wave and spin-Peierls order, is discussed.
Fagot-Revurat
Y
Physikalisches Institut, Universitat Stuttgart, 70550 Stuttgart, Germany.
Mehring
M
Kremer
RK