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MA: Fachverband Magnetismus

MA 24: ThyssenKrupp Dissertations-Preis 2011 der AG Magnetismus

MA 24.1: Talk

Tuesday, March 15, 2011, 13:30–13:50, HSZ 04

Current-Induced Magnetization Dynamics of Ferromagnetic Nanostructures — •Lars Bocklage — Institut für Angewandte Physik, Universität Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany

New concepts of magnetic memories use electrical currents to control themagnetization in sub-micron magnetic elements. Magnetic domain walls and vortices are of special interest as they are controllable magnetization configurations in thinnanowires and squares. Domain walls and vortices can be excited by currents toshow resonant dynamics. These magnetization patterns can be described as quasiparticles.Time-resolved X-ray microscopy is used to track their motion [1,2]. Bycomparison of the experimental data with analytical theories we can deduce thecontributions of spin transfer-torque and Oersted fields to the driving force anddetermine intrinsic parameters of domain walls like their mass or their damping time.Domain walls in nanowires can be pinned by constrictions. Their pinning anddepinning fields show stochastic behavior and depend on the geometry of the wires.This behavior is given by the accessible domain wall types in the vicinity of a notch[3]. For current-induced domain-wall motion we observe a dependence of thedepinning probability on the rise time of current pulses [4]. The analytical descriptionshows that for short rise times a strong force acts on the domain wall which arisesfrom the time derivative of the current. No classical analogy exits for this contributionto the force.

[1] L. Bocklage, B. Krüger, R. Eiselt, M. Bolte, P. Fischer, and G. Meier, Phys. Rev.B 78, 180405(R) (2008)

[2] M. Bolte, G. Meier, B. Krüger, A. Drews, R. Eiselt, L. Bocklage, S. Bohlens, T.Tyliszczak, A. Vansteenkiste, B. van Waeyenberge, K. W. Chou, A. Puzic, andH. Stoll, Phys. Rev. Lett. 100, 176601 (2008)

[3] M.-Y. Im, L. Bocklage, P. Fischer, and G. Meier,Phys. Rev. Lett. 102, 147204 (2009)

[4] L. Bocklage, B. Krüger, T. Matsuyama, M. Bolte, U. Merkt, D. Pfannkuche,and G. Meier, Phys. Rev. Lett. 103, 197204 (2009)