Magnetic Investigations of Thin Films of Oxides

This thesis describes ZnO thin films that were doped with a variety of dopants including transition metals (TMs) and rare earth elements (RE) but also non TM-dopants. These so-called d0 magnetic materials were investigated because they are promising emerging candidates for the development of spintronics. The aim was to enhance and investigate the origin of ferromagnetism in these materials by analysing and studying the structure, magnetic and magneto-optic properties.
The large magnetisation produced by the implantation of Krypton ions in ZnO is found to be dependent on the polarity of ZnO films. This result was obtained after evaluating the Kr implantation into different systems, O and Zn polar thin films and a ZnO wafer. Raman scattering was used to evaluate the crystalline damaged due to implantation and distinguish the scattering from amorphous regions in grain boundaries and the scattering from point defects. The effects on the structure and the magnetic properties of Co and Eu implanted ZnO thin films, made by pulsed laser deposition (PLD), are experimentally investigated. The large magnetisation was found to arise due to defects after implantation. However, the defects were recovered after annealing the films at 600o C in air, and another type of magnetisation was observed, where no clusters or any related oxide phases have been detected.
The structural and magnetic properties of Co-doped ZnO thin films, made by PLD, with either metallic Co, CoO or Co3O4 precursors have been investigated. These films were made at base pressure 2× 10-5 Torr, and further higher oxygen pressures of 1× 10-4 Torr, 1 × 10-3 Torr, 1 × 10-2 Torr, and 1 × 10-1 Torr. There were certain features of the films for which, films made from the metallic Co target, behave quite differently to those made from CoO and Co3O4 targets.