All-optical probe of magnetization dynamics in exchange biased bilayers on the picosecond timescale |
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Authors: | Weber M C Nembach H Blomeier S Hillebrands B Kaltofen R Schumann J Carey M J Fassbender J |
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Institution: | (1) Fachbereich Physik and Forschungsschwerpunkt MINAS, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 56, 67663 Kaiserslautern, Germany;(2) Institut für Dünnschichtsysteme der Mikroelektronik, IFW Dresden, 01171 Dresden, Germany;(3) Hitachi Global Storage Technologies, San Jose Research Center, 650 Harry Rd., San Jose, CA 95120, USA;(4) Institut für Ionenstrahlphysik und Materialforschung, Forschungszentrum Rossendorf, 01314 Dresden, Germany |
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Abstract: | All-optical control of the magnetization of polycrystalline exchange bias
bilayer systems is achieved using short picosecond laser pulses. Due to the
photoexcitation, the spin temperature across the interface between the
ferromagnetic and antiferromagnetic layer is elevated, resulting in a
collapse of the interfacial exchange coupling. Thus, within the first 10 ps,
a fast reduction of both the exchange bias field and the coercive field is
observed for three different exchange bias systems comprising both different
ferromagnets and antiferromagnets. The fast thermal unpinning is followed by
a slower heat diffusion dominated relaxation process, which strongly depends
on the thermal conductivity of the used buffer layers and substrates. The
fast optical unpinning can be understood in terms of an internal anisotropy
pulse field capable of triggering ultrafast precessional magnetization
dynamics of the ferromagnetic layer, which makes heat-assisted coherent
magnetization rotation feasible. |
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