Ferromagnetism in Ag doped TiO2 nanoparticles synthesized by sol-gel technique

Ag doped TiO2 (Ag=1, 5, 10, 14 at-wt%) nanoparticles were prepared by sol-gel technique and annealed at 700°C in air atmosphere. An anatase to rutile phase transformation is observed in the 14% Ag:TiO2 sample. Microscopic images show Ag clusters at the grain boundaries when the dopant concentration was increased beyond 5 at-wt%. The bandgap of the TiO2 samples becomes narrower with Ag doping, indicating incorporation of Ag in the substitutional sites of the host lattice. Here, we have also studied the effect of Ag doping on the magnetic properties of the samples. The M-H loop indicates that ferromagnetic ordering is maximum in the 5% Ag:TiO2 sample. We have explained the ferromagnetic ordering by Bound Magnetic Polaron (BMP) theory and concluded that the spin ordering in the samples is an intrinsic phenomenon occurring due to the substituted Ag+ ion in the TiO2 lattice.