Structures and magnetic properties of wurtzite Zn1-xCoxO dilute magnetic semiconductor nanocomposites

Cobalt-doped ZnO dilute magnetic semiconductor nanocomposites Zn1-xCoxO with Co concentrations from 0.02 to 0.25 were prepared by the sol-gel method. The magnetic measurement shows paramagnetic behavior for all the samples. The structures of these composites were investigated by x-ray diffraction and fluorescence x-ray absorption fine structure spectroscopy. It is indicated that at low Co concentration (x <= 0.05), the Co atoms are incorporated into the ZnO lattice and located at the substitutional sites of the Zn atoms. At higher Co doping concentration (x >= 0.10), the secondary phase Co3O4 is precipitated. Correlating the magnetic behavior with the structural properties of the Zn1-xCoxO nanocomposites, the authors interpret the paramagnetism to be intrinsic in nature as a result of the low effective doping of Co in ZnO and the lack of oxygen vacancies. (c) 2007 American Institute of Physics.