Regensburg 2013 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 12: Focus Session: Terahertz Spintronics
MA 12.3: Topical Talk
Dienstag, 12. März 2013, 10:30–11:00, H10
Engineering of terahertz spin currents in magnetic heterostructures — •T. Kampfrath1, M. Battiato2, P. Maldonado2, G. Eilers3, J. Nötzold1, S. Mährlein1, V. Zbarsky3, I. Radu4, F. Freimuth5, Y. Mokrousov5, S. Blügel5, M. Wolf1, P. M. Oppeneer2, and M. Münzenberg3 — 1Fritz Haber Institute, Berlin, Germany — 2University of Uppsala, Sweden — 3University of Göttingen, Germany — 4BESSY II, Helmholtz Center Berlin, Germany — 5Forschungszentrum Jülich, Germany
One goal of spintronics research is the controlled transport of spin-polarized electron bunches through a solid, preferably at frequencies reaching the so far unexplored terahertz (THz) regime. Here, we show, by experiment and theory, that femtosecond spin currents can be manipulated by using suitable magnetic heterostructures. A femtosecond laser pulse is employed to trigger spin transport from a ferromagnetic Fe thin film into a nonmagnetic cap layer with either low (Ru) or high (Au) electron mobility. To detect the transient spin current js(t), we make use of the inverse spin Hall effect that converts js(t) into a charge current jc(t). By sampling the subsequently emitted electromagnetic THz transient in the time domain, the temporal structure of the femtosecond spin current can be determined. We find that the Fe-Ru bilayer yields a considerably longer js(t) because electrons are injected in Ru d states that have a much lower mobility than Au sp states. Thus, THz spin current pulses can be shaped by tailoring magnetic heterostructures, which may open a route to engineering high-speed spintronic devices.