Variation of structural, optical and magnetic properties with Co-doping in Sn1−xCoxO2 nanoparticles

Abstract

Pure and Co-doped SnO2 nanoparticles with various Co concentrations of 1%, 3%, 5%, 7% and 10% have been synthesized by the coprecipitation technique. X-ray diffraction and field emission scanning electron microscope equipped with energy dispersive spectrometer were performed to analyze the crystal structure and check the possible presence of any impurity elements in the nanocrystals. Optical absorption and photoluminescence spectra were used to confirm that the Co is substituted at the Sn site in SnO2 matrix and does not form metallic clusters and other oxide phases for Sn1−xCoxO2 (x=0.00–0.10). Meanwhile, it was revealed that the energy band gap decreases and emission peak blue-shifts with the increasing Co-doping. Magnetization measurement shows that the low Co-doping (x≤0.03) develops the ferromagnetism and paramagnetism, but they are weakened by the higher Co-doping due to the formation of antiferromagnetic superexchange coupling among neighboring Co ions. The observed magnetic behaviors support the bound magnetic polarons model.