Static Spin Freezing inNaV2O5Detected by Muon Spin Relaxation

Abstract

Static spin freezing at $T\ensuremath{\sim}11\mathrm{K}$ was detected by muon spin relaxation ( $\ensuremath{\mu}\mathrm{SR}$) measurements of ${\mathrm{NaV}}_{2}{\mathrm{O}}_{5}$, which is widely considered to have a spin-singlet state below 35 K. This spin freezing is suppressed in charge-doped Na deficient samples ${\mathrm{Na}}_{x}{\mathrm{V}}_{2}{\mathrm{O}}_{5}$ with $x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.99$ and 0.90, in which spin gap formation is also suppressed. We discuss a few different scenarios to interpret this spin freezing.