Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 24: Spindynamics / Switching II
MA 24.4: Vortrag
Donnerstag, 29. März 2007, 11:00–11:15, H23
Ultrafast dynamics of the magnetic phase transition on FeRh — •Ilie Radu1,2, Alexander Weber1, Paul Ramm1, Christian Stamm2, Torsten Kachel2, Niko Pontius2, Jan Thiele3, Hermann Dürr2, and Christian Back1 — 1Institut für Experimentelle Physik, Universität Regensburg, Germany — 2BESSY GmbH, Berlin, Germany — 3Hitachi Global Storage Technologies, San Jose, U.S.A.
The laser-induced dynamics of the antiferromagnetic (AFM) to ferromagnetic (FM) phase transition of the FeRh alloy is studied by two complementary experimental techniques: the time-resolved magneto-optical Kerr effect (MOKE) and the time-resolved X-ray circular magnetic dichroism (XMCD). The transient MOKE data reveal an ultrafast onset of the FM ordering within 500 fs after femtosecond laser excitation. This result points to an electronically-driven AFM-FM transition since the lattice heating and the resulting lattice expansion evolve on a longer time scale. From the time-resolved XMCD spectra we obtain a similar dynamics for the Fe and Rh magnetic moments with a rise-time of 100 ps, which seems to contradict the dynamic MOKE data. The possible origin of this discrepancy will be discussed in terms of excitation and detection mechanisms in MOKE and XMCD. Due to the large magnetic moment of FeRh established in the FM state, one can use the ultrafast phase transition to trigger a coherent magnetization precession of a thin ferromagnetic film in contact with FeRh. Here, we present first pump-probe MOKE measurements of such a double layer system of CoPd/FeRh, that show two oscillatory components at 60 GHz and 80 GHz.