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MA: Fachverband Magnetismus
MA 54: Spin Excitations I
MA 54.1: Talk
Thursday, March 17, 2011, 15:00–15:15, HSZ 04
An X-ray View on Ultrafast Magnetization Switching of GdFeCo — •Ilie Radu1,2, Kadir Vahaplar1, Christian Stamm2, Torsten Kachel2, Niko Pontius2, Hermann Dürr2,5, Thomas Ostler3, Joe Barker3, Richard Evans3, Roy Chantrell3, Arata Tsukamoto4, Akiyoshi Itoh4, Andrei Kirilyuk1, Theo Rasing1, and Alexey Kimel1 — 1IMM/SSI Radboud University Nijemegen, The Netherlands — 2Helmholtz-Zentrum Berlin, BESSY II, Germany — 3Department of Physics, University of York, United Kingdom — 4College of Science and Technology, Nihon University, Japan — 5SLAC National Accelerator Laboratory, USA
Exchange interaction is the strongest force in magnetism, being ultimately responsible for ferromagnetic or antiferromagnetic spin order. How do spins react after being optically perturbed on a timescale faster than the exchange interaction? Here, we demonstrate that femtosecond measurements of ferrimagnetic GdFeCo alloy using X-ray magnetic circular dichroism provide revolutionary new insights into the problem of magnetism on timescales pertinent to the exchange interaction. In particular, we show that upon fs optical excitation the ultrafast spin reversal of GdFeCo - a material with antiferromagnetic coupling of spins - occurs via a transient ferromagnetic state. The latter one emerges due to different dynamics of Gd and Fe magnetic moments: Gd switches within 1.5 ps while it takes 300 fs for Fe. These observations, supported by atomistic simulations, present a novel concept of manipulating magnetic order on timescales of the exchange interaction. Funding from EU through UltraMagnetron programme is acknowledged.