Effect of annealing conditions on the magnetism of Vanadium-doped TiO2 powders

In order to investigate the effect of annealing conditions on the structural and magnetic properties, Vanadium-doped TiO2 powders have been synthesized by a sol–gel technique in air and then postannealed in argon atmosphere at different temperatures from 500 to 850 ∘C. It is shown that the samples transform from anatase phase to rutile phase of TiO2 as the annealing temperature increases to 700 ∘C. Meanwhile, room temperature ferromagnetism is enhanced after postannealing in argon atmosphere and the ferromagnetism increases with annealing temperatures. A plausible explanation for the enhancement of ferromagnetism with annealing temperatures is presented in terms of bound magnetic polaron model.