Anomalous magnetic properties of VOx multiwall nanotubes

Abstract

Basing on the high frequency (60 GHz) electron spin resonance (ESR) and magnetic susceptibility study of the VOx multiwall nanotubes (VO x-NTs) in the range 4.2-300 K we report the ESR evidence of the presence of the antiferromagnetic V4+ dimers in VOx-NTs and the observation of an anomalous low temperature (T<50 K) growth of the magnetic susceptibility for V4+ quasi-free spins, which obey power law χ(T)∼1/Tα with the exponent α0.6. The estimates of the concentrations for various spin species (clusters) indicate that the non-interacting dimers should be an essential element in the VO x-NTs structure. The possibility of the disorder driven quantum critical regime in VOx-NTs is discussed. © 2010 IOP Publishing Ltd.