Large magnetic moment observed in Co-doped ZnO nanocluster-assembled thin films at room temperature

Co-doped ZnO nanocluster-assembled films were deposited by nanocluster-beam deposition. Zn0.986Co0.014O nanoclusters remained wurtzite in structure with size of 5nm. Compared with bulk ZnO, a blueshift of 0.28eV was observed in the absorption edge of the film. Two photo-luminescence bands at 378 and 510nm were detected. Room-temperature ferromagnetism was observed in doped ZnO nanocluster-assembled film. Moreover, it exhibited a large saturated magnetization of 1.4μB∕Co and increased to 3.65μB∕Co after the film was annealed. The possible mechanisms on the observed ferromagnetism and enhanced magnetic moment were discussed.

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