Influence of annealing atmosphere on room temperature ferromagnetism of Mn-doped ZnO nanoparticles

► Zn0.92Mn0.08O nanoparticles were synthesized by co-precipitation technique, and annealed in H2, CO, Ar and O2, respectively. ► Room temperature ferromagnetism was found in sample annealed in H2 and CO, respectively. ► The higher the carrier concentration, the larger the shift to the high energy direction in the optical absorption spectra. ► Singly ionized oxygen vacancies play an important role in the origin of ferromagnetism. ► We decomposed visible emission peaks into the green emission band and yellow emission band by Gaussian fitting.