The effect of additional doping with Nb, Al or Cu on ferromagnetism and conductivity in V-doped TiO2 powders

Rutile Ti0.94V0.06O2 and Ti0.93V0.06M0.01O2 (M=Nb, Al, and Cu) polycrystalline powders are synthesized by the standard solid-state reaction method. The room-temperature saturation magnetization and resistivity of Ti0.94V0.06O2 powders are 2.5×10−3 emu/g (≈0.60×10−3μB/V) and above 107 Ω cm, respectively. The ferromagnetism weakens remarkably, and the conductivity enhances after additional doping with Nb or Al in V-doped rutile TiO2 powders. The room-temperature magnetization and resistivity of Ti0.93V0.06Cu0.01O2 powders are 2.1×10−3 emu/g and 1.26×106 Ω cm, respectively. Based on analysis for chemical valence of dopants by the x-ray photoelectron spectroscopy spectra, and using the bound magnetic polaron model, the microscopic mechanisms of ferromagnetism in V-doped rutile TiO2 powders with or without additional dopants are discussed in detail.