Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 35: Spin-Dynamics / Spin-Torque IV
MA 35.11: Vortrag
Donnerstag, 26. März 2009, 18:00–18:15, HSZ 04
Characterizing half-metallicity via magnetization dynamics on ultrafast timescales — •Andreas Mann1, Henning Ulrichs1, Jakob Walowski1, Markus Münzenberg1, Jan Schmalhorst2, Andy Thomas2, Andreas Hütten2, and Günter Reiss2 — 1I. Physikalisches Institut, Universität Göttingen, Germany — 2Department of Physics, Universität Bielefeld, Germany
We study the magnetization dynamics of potential half-metals probed by the time-resolved magneto-optical Kerr effect (TRMOKE) using a femtosecond laser pump-probe setup (temporal resolution: 50 fs). Half metals are promising candidates for the development of so called ’spintronic’ devices, because they possess a minority-spin band gap at the Fermi level and are therefore 100 % spin-polarized. The magnetization dynamics in ferromagnetic metals are generally marked by two characteristic timescales, a short demagnetization time τm of several hundred fs and a relaxation time τe in the ps range. In the special case of a half metal, the minority-spin band gap blocks the Elliot-Yafet scattering and thus slows down the demagnetization. The enlarged τm of a few ps to ns which is governed by anisotropy fluctuations can be measured in our setup and indicates a half-metallic behaviour of the sample. More in detail, our experiments imply that the band gap of a half metal also has a subtle influence on the magnetization dynamics on the ultrafast timescale, evident in a steplike feature. We present an expansion of the three temperature model by Beaurepaire et al.. We gratefully acknowledge the support by the DFG SPP 1133: ”Ultrafast magnetization processes”.