Mn-doped ZnO nanotubes: from facile solution synthesis to room temperature ferromagnetism

Mn-doped ZnO nanotubes have been synthesized via a simple, soft solution route at 70 degrees C without any surfactants and templates using zinc acetate, manganese acetate and sodium hydroxide as raw materials. The nanotubes are of 1.0-2.5 mu m in length, 300-500 nm in outer diameter, and 50-80 nm in wall thickness. The microstructure related to Mn doping in the ZnO matrix was characterized by X-ray diffraction, Raman scattering and X-ray photoelectron spectroscopy. The formation mechanism of the tubes, as well as the effect of the reaction temperature and Mn dopants on the structures and magnetic properties, was analyzed in detail. Room temperature ferromagnetic behavior was observed in Mn-doped ZnO nanotubes with a Mn concentration of 3% in atomic ratio; however, ferromagnetism is gradually suppressed by paramagnetic effect with increasing Mn concentration up to 6%. The origin and reduction of the ferromagnetism may be closely associated with the portion of Mn compounds containing Mn atoms in different oxidation states.