Dr. Martin Gradhand
Doctoral Thesis: The extrinsic spin hall effect
An ab initio description of the extrinsic spin Hall effect induced by the skew scattering mechanism at nonmagnetic impurities in nonmagnetic metals is presented. This effect opens the opportunity to create spin currents in nonmagnetic systems without the problem of spin injection from a ferromagnetic lead. For applications systems combining a strong spin Hall effect with a long spin diffusion length are desirable. Based on the presented material specific method dilute metallic alloys are identified providing both conditions essential for an application. The technique is based on a relativistic Korringa-Kohn-Rostocker Green’s function method in the framework of density functional theory. The electronic structure of an ideal crystal and a perturbed system is used to calculate the scattering probabilities. The electronic and spin transport is described by a linearized Boltzmann equation including spin-flip processes.
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Diploma Thesis: Tunnel Magneto-resistance (TMR) with Amorphous Electrodes
The tunneling magnetoresistance (TMR) effect measured in junctions consisting of an insulator between two ferromagnets have a variety of applications like read heads in hard disks and magnetic random access memory (MRAM). The aim of this work was to investigate the influence of structural disorder on the tunneling magnetoresistance in systems from Fe/MgO/Fe. The finite thickness of the magnetic iron was also considered.
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Research Internship: Classical Physics as a Limit of Quantum Mechanics
The aim of this work was to analyze the quantum-mechanical time development of a wave packet in different simple potentials. In special we tried to find the the quasi classical behavior of the system and of the expectations values as limit from the quantum-mechanical description. This is possible, since classical physics must be contained as a limit in quantum mechanics.
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