Degree Granting Department
Casey W. Miller
Magnetite, Magnetothermopower, Spin caloritronics, Spin Seebeck effect, Spintronics, Spin valve
Magnetic oxides have become of interest source for spin transport devices due to their high spin polarization. But the real applications of these oxides remains unsatisfactory up to date, mostly due to the change of properties as a result of nano structuring. Magnetite (Fe3O4) is one such a material. High Curie temperature and the half metallicity of Fe3O4 make it a good potential candidate for spin transport devices. Studies have shown that the nano structuring Fe3O4 changes most of it's important properties. This includes high saturation magnetization and drop of conductivity by a few orders of magnitude in Fe3O4 thin films.
In this study, we have successfully grown Fe3O4 by reactive sputtering and studied the effect of transition metal buffer layers on structural, transport, and magnetic properties of Fe3O4. It is shown that the lattice strain created by different buffer layers has major impacts on the properties of Fe3O4 thin films. Also for the first time the magnetic force microscopic measurements were carried out in Fe3O4 thin films through Verwey transition. MFM data with the magnetization data have confirmed that the magnetization of Fe3O4 thin films rotate slightly out of the plane below the Verwey transition.
Fe3O4 thin films were also successfully used in fabricating spin valve structures with Chromium and Permalloy. Here, the Fe3O4 was used to generated the spin polarized electrons through reflection instead of direct spin injection. This is a novel method that can be used to inject spins into materials with different conductivities, where the traditional direct spin injection fails. Also the effect of growth field on Fe3O4 and Fe3O4/Cr/Py spin valves were investigated. In Fe3O4 the growth field induced an uni-axial anisotropy while it creates a well defined parallel and anti-parallel states in spin valves.
Magneto thermal phenomenon including spin dependent Seebeck effect, Planar Nernst effect, and Anomalous Nernst effect were measured in ferromagnetic thin films and spin valves. Spin dependent Seebeck effect and planar Nernst effect were directly
compared with the charge counterpart anisotropic magneto resistance. All the effects exhibited similar behavior indicating the same origin, namely spin dependent scattering.
Scholar Commons Citation
Jayathilaka, Priyanga Buddhika, "Spin Dependent Transport in Novel Magnetic Heterostructures" (2013). USF Tampa Graduate Theses and Dissertations.