Magnetic and structural properties of Co doped ZnO nanowires prepared by heat treatment of electrospun PVA nanofibers containing Zn and Co acetates

We report the synthesis of inter-twined ZnO nanowires doped with Co by electrospinning polyvinyl alcohol along with metal oxide precursors followed by heat treatment in air at 550 °C for 90 min. This heat treatment removed PVA from the samples and ensured crystallization of 1-dimensional metal oxide nanostructure. X-ray diffraction (XRD) patterns also confirmed single phase wurtzite-type ZnO structure in samples with 3 wt% Co. Traces of Co₃O₄ could be observed in XRD patterns of samples with 5 wt% Co. However, micro-Raman spectra clearly indicate the presence of Co₃O₄ in samples with Co content more than 2 wt% which is also supported by electron paramagnetic resonance studies. UV–Vis absorption studies showed an increase in band gap energy with substitution of Co in ZnO structure. Field dependent magnetization curves recorded at room temperature revealed weak room temperature ferromagnetism with considerable paramagnetic component. The results are used to understand the origin of magnetism in this alloy and the extent of possible doping of Co in ZnO nanofibers.