Dresden 2014 – scientific programme
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MA: Fachverband Magnetismus
MA 22: Magnetization Dynamics I
MA 22.8: Talk
Wednesday, April 2, 2014, 11:30–11:45, HSZ 401
Ultrafast demagnetisation dynamics in Cu-doped Permalloy — •Sadashivaiah Sakshath1, Oliver Schmitt1, Daniel Steil1, Moritz Barkowski1, Sabine Alebrand1, Ute Bierbrauer1, Emrah Turgut2, Patrik Grychtol2, Justin Shaw3, Roman Adam4, Chan La-O-Vorakiat2, Hans T. Nembach3, Claus M. Schneider4, Margaret M. Murnane2, Henry C. Kapteyn2, Thomas J. Silva3, Stefan Mathias1, and Martin Aeschlimann1 — 1TU Kaiserslautern, Germany — 2JILA, University of Colorado, USA — 3NIST, Boulder, USA — 4Forschungszentrum Jülich, Germany
Permalloy doped with Copper presents itself as an interesting system for investigations of ultrafast demagnetisation dynamics as the exchange interaction is tuned [1]. Here, we perform fluence dependent TR-MOKE measurements for different Copper concentrations. In pure Permalloy, where exchange coupling is strong, and the Curie temperature is high, the demagnetisation time constant (τm) increases monotonously as the magnetization is quenched. These dynamics gradually change with increasing copper concentration. First, the total demagnetization times become slower, and second we observe a drastic reduction of τm at high quenching values, similar to the predictions of the M3TM model [2]. The influence of varying exchange coupling on the measured ultrafast demagnetization rates is discussed.
[1] S. Mathias et al., PNAS 109, 4792 (2012)
[2] B. Koopmans et al., Nature Materials 9, 259 (2010)