Superparamagnetism in undoped ZnO nanorods

Nanostructured zinc oxide nanorods were prepared by the oxidation of nanostructured zinc films by thermal evaporation of metallic zinc. XPS measurement showed that the peak intensity of adsorbed oxygen is comparatively higher compared to intrinsic oxygen vacancies. The electrical conductivity measurements showed that the conduction mechanism in ZnO nanorods is due to the hopping of charge carriers. Magnetic measurements showed neither hysteresis nor remanence indicating superparamagnetism in the samples. The hopping of charge carriers and superparamagnetism in undoped ZnO is attributed to presence of adsorbed oxygen gas molecules in the surface.