Abstract
This thesis is to explore spin-dependent transport current, induced and intrinsic magnetism in bulk uranium as well as in thin films. Uranium, having the largest spin-orbit coupling among naturally existing elements, has potential to achieve high-performance in applications of spin-dependent transport.First, we will calculate the electronic structure for different U crystal phases using the fully-relativistic Korringa-Kohn-Rostoker (KKR) Green’s function method within the density functional theory (DFT). The intrinsic spin conductivity is described via an integral of the Berry curvature of all occupied states over the Brillouin zone. The extrinsic spin Hall effect (skew scattering) is studied by means of the semi-classical Boltzmann formalism. Comparing the results from these two mechanisms it is found that the hcp-U shows the largest efficiency of charge-to-spin conversion.
Considering the spin Hall effect in thin films, there will be spin accumulation at the surfaces and induced magnetism across the thin film. The spin accumulation in light as well as heavy metals is calculated using the semi-classical Boltzmann equation. Comparing the resulting spin accumulation with three different approximations, we identify the contributions to the spin accumulation in the metals with different strengths of spin-orbit coupling.
Using a DFT-KKR solver based on the Bogoliubov-de Gennes equation within the Bardeen–Cooper–Schrieffer theory, the superconducting state can be described as well. First, we calculate the electronic structure for the superconducting state of gamma-U and discuss this gap anisotropy of the f-electron material. In addition, an in-gap bound state can be induced by magnetic impurities, which is called a Yu-Shiba-Rusinov state. We investigate this impurity-induced state by placing a magnetic Mn atom on a Pd thin film and compare our results to experimental observations. The effect of distance between the surface and the Mn impurity on the YSR states will be discussed in detail.
| Date of Award | 24 Feb 2022 |
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| Original language | English |
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| Supervisor | Martin Gradhand (Supervisor) |