Static Spin Freezing in NaV2O5 Detected by Muon Spin Relaxation

Static spin freezing at T∼11 K was detected by muon spin relaxation ( μSR) measurements of NaV2O5, which is widely considered to have a spin-singlet state below 35 K. This spin freezing is suppressed in charge-doped Na deficient samples NaxV2O5 with x=0.99 and 0.90, in which spin gap formation is also suppressed. We discuss a few different scenarios to interpret this spin freezing.