Effects of Tungsten Doping on Magnetic and Material Properties of VO₂/Ni Bilayers

Magnetic hybrid materials show increasing promise as candidates for magnetic storage and magnetic sensors under a wide range of operating environments. Strain coupled materials are a type of magnetic hybrid materials that show a strong potential for precise control over magnetic properties. Vanadium oxides are a class of compounds which have structural phase transitions (SPTs) at various temperatures, making them ideal candidates in the fabrication of hybrid materials of this nature. Previous work has shown sputtered vanadium oxide/ferromagnetic bilayers have large changes in magnetization and coercivity at the vanadium oxide transition temperature. In this study, a sol-gel synthesis technique was used to fabricate W-doped VO₂/Ni bilayers. Doping with W allows for the VO₂ transition temperature to be lowered in an easily controlled manner, making it more viable for various applications. The effects of this doping technique on the material and magnetic properties of the VO₂ layers are investigated. We find a stabilization of the rutile phase of VO₂, and formation of V₂WO₆. VO₂/Ni bilayers show a sharp decrease in the coercivity and increase in the magnetic moment at the VO₂ SPT. W doping decreases the temperature of these magnetic effects and also decreases their magnitude.