Microstructure and Magnetic Properties of Cobalt-Doped SnO₂ Nano-Powders

Cobalt-doped SnO2 nano-powders (Sn1-xCoxO2) are fabricated by wet chemical method. It is found that cobalt exists as an ionic state instead of pure metal state. There is no other impurity phase in the samples except for rutile type SnO2. With the increase of cobalt concentration, the crystalline size decreases, the optical absorption spectra red-shiftes, and the band gap decreases linearly. The decrease of magnetic moment per cobalt atom with the increase of cobalt concentration could be attributed to the increased number of cobalt atoms occupying adjacent cation lattice positions that result in antiferromagnetic alignment.