Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 24: Spindynamics / Switching II
MA 24.3: Vortrag
Donnerstag, 29. März 2007, 10:45–11:00, H23
Ultrafast magnetization dynamics probed by anisotropic magnetoresistance — •Santiago Serrano-Guisan1, Hans-Werner Schumacher1, Karsten Rott2, and Günter Reiss2 — 1Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116, Braunschweig, Germany — 2University of Bielefeld, Department of Physics, Universitätsstr. 25, D-33615 Bielefeld, Germany
We study ultrafast magnetization dynamics and relaxation of a single ferromagnetic layer by time resolved measurements of the anisotropic magnetoresistance (AMR). The samples consist of a 5 nm Ta seed layer, 5 nm permalloy (Fe19Ni81) and a 3 nm Al cap layer. The films are microstructured into disks of 4-6 micrometer diameter and are contacted by coplanar wave guides for ultra fast AMR detection. The samples show an AMR ratio around 0.25% and the typical cos2 angular dependence. Ultrafast magnetic excitation field pulses (rise time ~ 75ps, fall time ~ 670ps and duration at half maximum ~ 230ps) are applied using a pulse line on chip. Additionally, in plane static magnetic fields are applied using external coils. The temporal variation of the AMR upon pulse excitation clearly reveals the damped precession of the magnetization of the permalloy disk. From comparison to macro spin simulations we derive a Gilbert damping parameter of 0.008 for the permalloy. This technique can be used to access the dynamics of a wide variety of microstructured magnetic thin film devices showing AMR.