Electron tunneling and spin dynamics and transport in crystalline magnetic multilayers

This thesis reports on electron transport and the magnetization dynamics of crystalline multilayers grown on Fe-whiskers(001) and clean GaAs(001) wafers by means of molecular beam epitaxy (MBE). The high quality magnetic multilayers with well defined interfaces are required to allow one to compare quantitatively the experimental results with the theoretical predictions.; The electrical properties of crystalline Fe/MgO/Fe-whisker structures were characterized by in-situ scanning tunneling spectroscopy. Far mast of the scanned area, the tunneling I-V characteristics have revealed a tunneling barrier of 3.6 V which corresponds to the perfect MgO layer. At negative bias voltages, the localized spikes in the tunneling current have been observed indicating ballistic transport in crystalline tunnel junctions. Kerr microscopy has shown, that the magnetization of Fe-whisker and Fe film are coupled via stray field of the Fe-whisker domain wall. Atom force microscope (AFM) operating in an external magnetic field was used to measure tunneling magnetoresistance (TMR). In some cases, the TMR reached nearly 100% at RT.; The spin dynamics were studied in the ultrathin Fe films grown directly on (4 x 6) reconstructed GaAs(001) wafers. FMR was used to determine the static and dynamic magnetic properties of Fe/Cr and Fe/Au multilayers. For Fe films covered by Cr, the extrinsic relaxation term has shown evidence of two-magnon scattering. The in-plane Gilbert damping includes both intrinsic and extrinsic contributions to the Gilbert damping parameter.; In the Fe/Au/Fe multilayers, where the static interlayer exchange coupling is negligible, the magnetizations are still coupled through the normal metal (NM) spacer by emitting and absorbing non-equilibrium spin currents. Ultrathin Fe layers in double layer structures, Fe/Au/Fe, acquire an additional interface Gilbert damping compared to Fe/Au samples. The additional non-local Gilbert damping can be described by the spin-pump and spin-sink concepts. The second ferromagnetic (FM) layer acts as a spin momentum sink. A semi-classical model of the spin momentum transfer in FM/NM structures was formulated. The model is based on the Landau-Lifshitz equation of motion and the exchange interaction in FM, and the spin diffusion equation in the NM spacer. The internal magnetic field is treated by employing Maxwell's equations. The theoretical calculations are tested against the experimental results.