Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 23: Magnetization / Demagnetization Dynamics II
MA 23.5: Vortrag
Mittwoch, 28. März 2012, 10:45–11:00, H 1012
Magnon magnetometry of non-linear spin-wave excitations — •Hans G. Bauer1, Georg Woltersdorf1, Peter Majchrak1, Thorsten Kachel2, and Christian H. Back1 — 1Department of Physics, University of Regensburg, 93040 Regensburg, Germany — 2Helmholtz-Zentrum Berlin, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
The understanding of non-linear magnetization dynamics is essential for the operation of many spintronics devices. In particular it is important to understand the flow of angular momentum.
We study experimentally a very simple and relevant system, a thin ferromagnetic film. Time resolved X-ray magnetic circular dichroism experiments allow us to determine precisely the number of magnons in a Permalloy sample. In doing so we show that commonly used models for non-linear resonance are actually not applicable at low bias fields.
A simple non-linear model allows us to find the threshold and associated critical modes that agree well with our experimental findings and with micro-magnetic simulations. Other non-linear properties such as the wave-vector dependent non-linear frequency shift and frequency-locking to half-integer multiples of the driving frequency are also discussed.
Our model is also applicable to 1st and 2nd order Suhl instability processes, demonstrating its general character.