Effects of W Doping in VO₂ on the Magnetic Properties of VO₂/Ni Heterostructures

The effects of tungsten (W) doping on the material properties of VO₂ films and the magnetic properties of VO₂/Ni bilayers were investigated. Doped VO₂ films are fabricated using a sol-gel synthesis technique. As seen in previous studies, the vanadium dioxide metal to insulator transition (MIT) is shifted to lower temperature and reduced in magnitude with increased W doping. While the impact on transport is quite dramatic, morphology of VO₂ is only slightly affected by W doping. We find that there is a stabilization of the rutile phase of VO₂ at room temperature and formation of a small amount of V₂WO₆ phase. VO₂/Ni bilayers show a sharp decrease in the coercivity and increase in the magnetic moment at the VO₂ structural phase transition. W doping decreases the temperature of these magnetic properties and also decreases their magnitude. The decreased magnitude of the magnetic effects, along with the stabilization of the rutile phase seen in the X-ray data, suggests that the degradation of the MIT is due to structural reasons and not solely because of added carriers to the system.