Ferromagnetism In Inhomogeneous Bulk samples Of Co-doped ZnO

We report on the effect of different gaseous environments (air, argon and Ar/H2) on the structural and magnetic properties of Zn0.98Co0.02O synthesized by the solid state reaction route. We have also studied the effect of different annealing times and temperatures on the as synthesized samples. M-H curves of the air sintered and the argon annealed samples show paramagnetic behavior whereas the samples annealed in the hydrogenated argon (Ar/H2) environment exhibit ferromagnetic property at room temperature. Based on the structural and magnetic properties it has been found that Co metal clusters are responsible for the observed room temperature ferromagnetism (RTFM) in the hydrogenated samples.