Berlin 2008 – scientific programme
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MA: Fachverband Magnetismus
MA 19: Spin Dynamics / Spin Torque I
MA 19.7: Talk
Wednesday, February 27, 2008, 15:30–15:45, EB 301
Homodyne Detection of Domain Wall Oscillations — Daniel Bedau1, Mathias Klaeui1, Stefan Krzyk1, •Katarzyna Buchta1, Ulrich Ruediger1, G. Faini2, and L. Vila2 — 1Department of Physics, University of Konstanz, Germany — 2CNRS, Phynano Team, Laboratoire de Photonique et de Nanostructures, Route de Nozay, France
Laterally confined magnetic domain walls behave like quasiparticles moving in an external potential well created by a mechanical constriction or a pinning defect. Spin torque effects allow to displace the domain wall quasiparticle electrically, by injecting an ac current the domain can be excited to resonate inside the potential well. As the domain wall oscillates, the resistance of the magnetic structure is modulated due to the anisotropic magnetoresistance in phase with the domain wall position. If the quasiparticle happens to be excited at the resonance frequency, the varying resistance will rectify the injected high frequency current and a DC voltage is developed across the structure. Using this technique we determined the resonance frequency of the domain wall. At resonance we observed a reduction of the depinning field of the domain wall for currents as low as 2×1010 A/m2, allowing us to determine the resonance frequency by a second method. The domain wall resonance frequency was measured for different external magnetic fields and was found to be proportional to the external field. By measuring the mean value of the resistance during excitation we identified the oscillation of the domain wall to be confined close to the potential minimum without a large-scale displacement.