Strominduzierte Magnetisierungsdynamik in einkristallinen Nanosäulen

This thesis presents experiments on the current-driven magnetization dynamics in nanopillars containing single-crystalline iron and silver layers. Spinpolarized currents are on the one hand origin of the giant magnetoresistance (GMR). Due to spin accumulation at the interfaces the current perpendicular to the plane (CPP) geometry results in special properties of the GMR. On the other hand, these currents give rise to the spin transfer torque (STT) by direct transfer of spin angular momentum to the magnetizations. This STT induces fundamentally new magnetization dynamics. The special properties of CPP-GMR and STT at the iron-silver interface are revealed by measurements of GMR, current-induced switching, and current-driven high-frequency excitations. They follow from a strong spindependence of the interface resistance. Results from nanopillars of a diameter of 70 nm are compared with models and computer simulations. Two-step magnetization switching and low-field high-frequency excitations are presented that arise from the interplay of the crystalline anisotropy of bodycenteredcubic iron layers and the STT. The current-induced magnetization dynamics of inhomogeneously magnetized elements are studied in nanopillars of 230 nm diameter. The vorticity of a magnetic vortex state can be imprinted by preparation at dc currents of different sign due to the Oersted field around the pillar. The vorticity is distinguishable by different resistance levels and qualitative changes in current-driven high-frequency excitations. Even a phase-locking of the vortex oscillations to external signals is possible because of the vortex‘ nonlinear properties.