Open Access

Andreas Prinz-Zwick

• In this thesis, the transport properties of the half-metallic Heusler alloy NiMnSb are investigated. For the electronic structure calculations, density functional theory, as implemented in SIESTA, was used. The transport calculations were performed with SMEAGOL, an implementation of the non-equilibrium Green's function formalism. For the clean NiMnSb structure, without lattice defects, we considered a scattering region consisting of up to four unit cells. A very high spin-polarization of over 95% for the current was found even for small scattering regions of merely two unit cells. All these calculations were performed with and without atomic relaxation, with the result that relaxation has only a minor influence on the transport properties. Furthermore, for a two-unit-cell scattering region, several calculations were performed that included lattice defects. The influence of the defects depends strongly on the defect type, as well as on the location of the defect. Finally alsoIn this thesis, the transport properties of the half-metallic Heusler alloy NiMnSb are investigated. For the electronic structure calculations, density functional theory, as implemented in SIESTA, was used. The transport calculations were performed with SMEAGOL, an implementation of the non-equilibrium Green's function formalism. For the clean NiMnSb structure, without lattice defects, we considered a scattering region consisting of up to four unit cells. A very high spin-polarization of over 95% for the current was found even for small scattering regions of merely two unit cells. All these calculations were performed with and without atomic relaxation, with the result that relaxation has only a minor influence on the transport properties. Furthermore, for a two-unit-cell scattering region, several calculations were performed that included lattice defects. The influence of the defects depends strongly on the defect type, as well as on the location of the defect. Finally also effects of electronic correlations were discussed, with the result that their influence on the transmission around the Fermi level is rather small.…