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MA: Fachverband Magnetismus

MA 22: Magnetization Dynamics I

MA 22.8: Vortrag

Mittwoch, 2. April 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 (τ_m) 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 τ_m 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)