Ferromagnetism in Transition Metal Doped Nanoscale Tin Dioxide

This thesis focuses on recent advancements in producing above room-temperature ferromagnetism in nanoscale tin dioxide powders using sol-gel based chemical methods with property-specific tailoring through magnetic transition metal dopant introduction, specifically iron and cobalt, as well as through modification of the processing conditions. The synthesis of these nanoparticles using the sol-gel method under aerobic conditions inherently eliminates the formation of transition metal clusters, which in this case could be ferromagnetic, helping to establish the intrinsic nature of the ferromagnetism. This process also allows excellent control over the doping concentration, permitting the examination of systematic changes in the magnetic as well as other physical properties with dopant incorporation. This thesis will show the development of room-temperature ferromagnetism in tin dioxide and how dopant concentration and processing conditions such as preparation temperature and environment affect the magnetic and other physical properties of the material. Highly sensitive techniques will be employed to rule out the presence of any impurity phases in addition to monitoring the oxidation state, coordination/neighborhood and movement/diffusion of the dopant within the host lattice. Whenever possible, likely mechanisms explaining the observed ferromagnetism will be discussed in relation to experimental data. A novel application of the Fe doped SnO2 system is also presented showing how these dilute magnetic semiconductor oxides can be attractive materials for many other new applications in addition to spintronics