Abstract
Magnetic oxides have been studied widely for the interesting physical properties and potential applications for spintronics. This thesis was focused on the novel magnetic oxides for spintronic applications, and based on the topics including: "cluster free, Co doped Y2O3 (Co: Y2O3) high diluted magnetic oxides (DMO) ", "Laser MBE grown SrRuO3 and Sr2RuO4 for realizing the spin polarized 2 dimensional electron gas (2DEG) and the spin polarized supercurrent", and "magnetic oxide yittrium iron garnet (YIG) combined with topological insulator (TI) for the study of spin pumping and spin-transfer-torque ferromagnetic resonance (ST-FMR) for novel spintronic devices". Spin Pumping in TI/ferromagnetic metal (TI/FM) heterostructures were studied before YIG-based heterostructures researches. For the cluster free, DMO of Co: Y2O3 grown by low temperature deposition, room temperature (RT) ferromagnetism was observed, and the saturation magnetic moment was modulated by oxygen vacancy concentration through post annealing process. Oxygen vacancies are shown to play a crucial role in ferromagnetic ordering, as defect centers in the bound magnetic polaron model to account for this DMO of medium band gap with low carrier concentration. For Laser MBE grown SrRuO3 and Sr2RuO4, we obtained good crystallinity of SrRuO3 films and reasonable RT resistivity. We also obtained good crystallinity of Sr2RuO4 films and very low residue resistivity, but without superconductivity, which might be sensitive and destroyed by the defects. More efforts are needed to acquire lower residual resistivity for the superconductivity. The metallic SrRuO3/SrTiO3 superlattice with good crystallinity was successfully grown, providing a matrix to studied spin polarized 2DEG. The spin pumping effect in high quality films of Bi2Se3/Fe3Si and Fe/Bi2Te3 were studied. At RT, large voltages due to the inverse spin Hall Effect (VISHE) were detected in Bi2Se3/Fe3Si and Fe/Bi2Te3. The spin Hall angle was calculated. The charge current densities of TI/FM are about 2-5 times higher than the Fe3Si/normal metal and Fe3Si/GaAs results, attributed to strong spin-orbit coupling inherent of TIs, demonstrating the high potential of exploiting TI-based structures for spintronic applications. High quality YIG films have been grown and characterized. The excellent crystallinity and low magnetic damping of YIG films ensure efficient spin transport measurements and spin pumping have been performed in Bi2Se3/YIG, Pt/YIG structures. We observed VISHE and large negative resonance field shifts. Moreover, ST-FMR has been demonstrated in Pt/YIG structures, providing a direction to developing novel devices for spintronic applications.