4.In summary, ZnO nanofibers were prepared via electrospinning and annealing in air or vacuum. XRD data show that there is no impurity phase in the wurtzite ZnO nanofibers. Raman data indicates the presence of defects in the wurtzite ZnO nanofibers. Room temperature ferromagnetism is observed in all the samples with maximum saturation magnetization value in samples annealed at 550 1C. Higher magnetization exhibited by vacuum annealed ZnO nanofibers establishes the role of O vacancies in the RTFM observed in this wurtzite ZnO nanostructure. The present studies not only provide evidence for the role of O vacancies in the observed RTFM in ZnO nanofibers but also provides a means to tailor the O vacancies in ZnO nanostructures by controlling the ambient during the heat treatment of electrospun ZnO/PVA composites.