Effect of Co/Fe co-doping in TiO2 rutile prepared by solid state reaction

We investigated the magnetic and structural properties of TiO2 rutile single- and codoped with Fe and Co prepared by a solid state reaction method. The concentrations of each dopant was varied from 0 to 5%. Most of the samples were ferromagnetic at room temperature. When Co or Fe was single-doped to 3%, only weak room temperature ferromagnetism was observed. But when 1% of Fe or Co was additionally co-doped, magnetic moment per magnetic ion, remnant magnetization, and coercivity were significantly enhanced compared to the single-doped case, and this behavior was observed up to 5% co-doping. The structural study showed the TiO2 rutile phase for all of the samples with second phases of Fe2TiO5 and/or CoTiO3 depending on the contents of Co and Fe, but no indication of Co or Fe metallic cluster was found. The micro composition analysis showed the linear correlation between Co and Fe concentrations, which is a result of enhanced incorporation of magnetic ions into TiO2 host when co-doped. The Mösbauer spectrum showed that the value of the hyperfine field is about 1.5 times as large as that of α-Fe indicating that the Fe impurities substituted into Ti atoms instead of forming iron clusters.