Characterization of Spintronic Systems using Soft X-ray spectroscopy

The subject of this dissertation revolves around soft x-ray spectroscopy of materials doped with 3d transition metals . More specifically, investigating the effects of synthesis techniques and the phenomena associated with subtle changes in synthesis technique resulting in key chemical changes. These materials have the potential to bring a new frontier of opportunity within electronic devices and enable critical new technologies. This investigation is done using two main techniques. Experimentally, spectra are mea- sured using high resolution synchrotron-based techniques, and these spectra are then com- pared to theoretical calculations to bring insights into the electronic structure, precise location of defect states, and band gap of promising materials for future devices. Using these techniques, a system based on the semiconductor In2O3 is examined first. With the same host material, and varying the 3d transition metal additions (Fe, Ni, Co, Mn), this allows the systematic study of a single synthesis technique with the major variable being the dopant atom. Results here show the successful substitution of iron into the host In2O3 lattice, with varying secondary states seen with the other three dopants. Notably, oxygen vacancies are found with iron substituting for indium within the structure, prompting a further investigation into these specific lattice defects. A system based on the semiconductor SnO2 is examined, now keeping two consistent codopant atoms, but varying the concentration of the Zn and Co additives. Through this, the effects of not only the concentration of the dopants can be seen, but using two atoms creates two distinct defect sites within the material. The ability to shift the location of oxygen vacancies within the material via annealing cycles during synthesis is displayed. Furthermore the dependency of ferromagnetic properties on oxygen vacancies adjacent to cobalt atoms substituting for tin within the lattice is found