Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 25: Invited Talks Woltersdorf / Meier / Rasing

MA 25.2: Hauptvortrag

Donnerstag, 28. Februar 2008, 12:30–13:00, EB 301

Time-Resolved Imaging of Domain-Wall and Vortex Motion Driven by Spin-Polarized Currents — •Guido Meier — Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg, Germany

Transmission x-ray microscopy can directly visualize the influence of a spin-polarized current on the magnetization of micro- and nanostructures. We investigate the stochastic motion of domain walls in curved wires and the motion of vortices in squares. To observe domain-wall motion pulses of nanosecond duration and high current density are send through permalloy wires and either move or deform the domain wall. Repetitive pulse measurements reveal the stochastic nature of current induced domain-wall motion. Via a micromagnetic code based on OOMMF including the spin-torque transfer model of Zhang and Li experiments are compared to theory. The simulations support the interpretation of the experimental results.
Sinusoidal high-density currents are applied to micrometer-sized permalloy squares containing ferromagnetic vortices. Spin-torque induced vortex gyration on the nanosecond timescale is observed. The phase of the gyration in structures with different chirality are compared to an analytical model and micromagnetic simulations, considering both alternating spin-polarized currents and the current’s Oersted fields. This analysis reveals that spin-torque is the main source of motion.
Supported by the DFG via SFB 508, SFB 668, and GK 1286 as well as by the U.S. DOE Contract No. DE-AC02-05-CH11231.