Berlin 2008 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 24: SYM Thin Film Magnetic Materials: Microstructure, Reaction and Magnetic Coupling III

MM 24.2: Invited Talk

Wednesday, February 27, 2008, 14:30–15:00, H 1058

Coherent Control of Spin Torque Dynamics — •Hans Werner Schumacher¹, Santiago Serrano-Guisan¹, Karsten Rott², Günter Reiss², Jürgen Langer³, and Berthold Ocker³ — ¹Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig — ²University of Bielefeld, Universitätsstr. 25, D-33615 Bielefeld — ³Singulus Nano Deposition Technologies GmbH, Hanauer Landstr. 103, 63796 Kahl am Main

We study time resolved precessional magnetization dynamics induced by spin momentum transfer in nanopillars of CoFeB/MgO/CoFeB magnetic tunnelling junctions (MTJ). Spin transfer torque precession of the CoFeB free layer is excited by ultra short current pulses (0.1 to 5 ns duration) with current densities around 10^6 A/cm2. The time resolved precession of the free layer is studied by measuring the time resolved magneto resistance change of the MTJ using a fast sampling oscilloscope. Our setup allows both to detect the spin torque precession during the current pulse and the magnetization ringing after pulse termination. From the decay of the precession we can derive the effective Gilbert damping parameter of the MTJ free layer. We show that by adapting the duration of the excitation pulse to integer multiples of the period of the spin torque precession the magnetization ringing can be coherently suppressed. Such coherent control of spin torque dynamics is a prerequisite for ultra fast ballistic spin transfer torque magnetization reversal.