Impact of annealing on morphology and ferromagnetism of ZnO nanorods

Room temperature ferromagnetism has been observed in ZnO nanorods prepared by hydrothermal method. Saturation magnetization of similar to 0.004 emu/g was measured in the nanorods with diameters of similar to 10 nm and lengths of below 100 nm, and the magnetization reduced with the increase of the size. Annealing of the samples at 900 degrees C in air completely transformed the nanorods into twinning structures and weakened the magnetizations. The mechanism of morphology transformation was discussed. Analysis indicates that the interstitial zinc at the surface may contribute to the ferromagnetism in ZnO nanorods. (C) 2008 American Institute of Physics.