Distinct spins of substituent Co in polycrystalline Co- and Cu-codoped ZnO magnetic semiconductors

Polycrystalline Zn(0.938)Co(0.062)O and Zn(0.928)Co(0.062)Cu(0.01)O oxides have been synthesized by solid state reaction. A single-phase wurtzite structure was formed in the polycrystalline samples with substituent Co and Cu in oxidation states of +2 and +1, respectively. The magnetization can be fitted with a paramagnetic Curie term, an antiferromagnetic Curie-Weiss term, and a diamagnetic constant. The results show that the substitution of Co at the Zn site does not occur randomly but Co ions appear to have a tendency to group, while the substitution of Cu at the Zn can reduce Co's grouping tendency, resulting in more isolated free Co ions. (C) 2008 American Institute of Physics.