Muon spin relaxation in NaV2O5 in its spin-Peierls phase

Depolarization measurements of muons have been carried out on NaV2O5 in the temperature range from 6 K up to 150 It. through the spin-Peierls transition at T-sp = 33 K. Surprisingly. the relaxation is fitted throughout to a stretched eponential, exp( - (lambda( T)t)(beta(T))). We observe a dramatic rise in the relaxation rate lambda below T-sp. On the other hand, the exponent beta is greater than 1 above the transition temperature but falls to below 1/3 at 6 K, as in frustrated systems. Furthermore, the fit of the data shows that a fraction of muons is rapidly dc polarized when implanted in the sample. (C) 2000 Elsevier Science B.V. All rights reserved.