Dresden 2011 – scientific programme
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MA: Fachverband Magnetismus
MA 38: Magnetization Dynamics IV
MA 38.5: Talk
Wednesday, March 16, 2011, 15:45–16:00, HSZ 403
Ultrafast Element-Specific Decoupling of Magnetization Dynamics in Permalloy — •Patrik Grychtol1,3, Chan La-O-Vorakiat1, Stefan Mathias1,2, Justin Shaw4, Roman Adam3, Hans Nembach4, Mark Siemens1, Steffen Eich2, Henry Kapteyn1, Margaret Murnane1, Claus M. Schneider3, Tom Silva4, and Martin Aeschlimann2 — 1Department of Physics and JILA, University of Colorado, Boulder, Colorado 80309-0440, USA — 2University of Kaiserslautern and Research Center OPTIMAS, 67663, Kaiserslautern, Germany — 3Institute of Solid State Research, IFF-9, Research Center Juelich, 52425, Juelich, Germany — 4Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado 80305-3328, USA
Elucidating the dynamic behavior of complex magnetic systems far from their thermal equilibrium is a topic of utmost scientific interest. In our work, we employ soft x-ray pulses from high-harmonic-generation to probe the dynamic response of thin permalloy films during an ultrafast optically driven demagnetization process [1]. We find that the demagnetization times for the elements Fe and Ni differ significantly, despite their strong exchange coupling in the thermodynamic equilibrium. We ascribe this difference to a breakdown of exchange interaction on the femtosecond timescale, a process that we further enhance by alloying permalloy with Cu. Our data shows that, in general, a site-specific spin environment must be considered to correctly describe ultrafast magnetization processes in compounds.
[1] La-O-Vorakiat et al., Phys. Rev. Lett. 103, 257402 (2009)