Abstract
We report an experimental and theoretical investigation on the room temperature ferromagnetism of Zn0.95Cu0.05O and Zn0.94Cu0.05M0.01O (M=Ni, Fe and Ag)Ni nanoparticles synthesized by sol-gel method. X-ray diffraction analysis reveals single hexagonal wurtzite; meanwhile the lattice parameters are found to be sensitive to the ionic radius of the doping elements and the crystallite size varies in the range 22-47 nm. Field emission scanning electron microscopy observations show particles with spherical shape for ZnO and semi-spherical shape for co-doped nanopowders. Magnetic measurements using SQUID reveal room temperature ferromagnetic ordering for doped and co-doped nanopowders with a lower saturation magnetization compared to Cu-doped ZnO. It is found that the co-doping has resulted in weakening the ferromagnetic phase at the expense of the paramagnetic. First-principles calculations indicate that only Cu and Fe codoped ZnO systems own ferromagnetism, which originated from the interaction between Fe-d and O-p electrons. However, all doped systems show positive formation energies indicating they are less stable than undoped ZnO.