Nature Nanotechnology | Letter|
Terahertz spin current pulses controlled by magnetic heterostructures
Nature Nanotechnology. doi:10.1038/nnano.2013.43
Authors: T. Kampfrath, M. Battiato, P. Maldonado, G. Eilers, J. Nötzold, S. Mährlein, V. Zbarsky, F. Freimuth, Y. Mokrousov, S. Blügel, M. Wolf, I. Radu, P. M. Oppeneer & M. Münzenberg
In spin-based electronics, information is encoded by the spin state of electron bunches1, 2, 3, 4. Processing this information requires the controlled transport of spin angular momentum through a solid5, 6, preferably at frequencies reaching the so far unexplored terahertz regime7, 8, 9. Here, we demonstrate, by experiment and theory, that the temporal shape of femtosecond spin current bursts can be manipulated by using specifically designed magnetic heterostructures. A laser pulse is used to drive spins10, 11, 12 from a ferromagnetic iron thin film into a non-magnetic cap layer that has either low (ruthenium) or high (gold) electron mobility. The resulting transient spin current is detected by means of an ultrafast, contactless amperemeter13 based on the inverse spin Hall effect14, 15, which converts the spin flow into a terahertz electromagnetic pulse. We find that the ruthenium cap layer yields a considerably longer spin current pulse because electrons are injected into ruthenium d states, which have a much lower mobility than gold sp states16. Thus, spin current pulses and the resulting terahertz transients can be shaped by tailoring magnetic heterostructures, which opens the door to engineering high-speed spintronic devices and, potentially, broadband terahertz emitters7, 8, 9.
Department of Physical Chemistry, Fritz Haber Institute, Faradayweg 4-6, 14195 Berlin, Germany
S. Mährlein &
Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
P. Maldonado &
P. M. Oppeneer
I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
V. Zbarsky &
Peter-Grünberg-Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
Y. Mokrousov &
Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489 Berlin, Germany
T.K., M.W., I.R. and M.M. initiated the project. T.K., J.N. and S.M. designed the experiment, performed the terahertz measurements and analysed the data. G.E., V.Z., I.R. and M.M. fabricated and characterized the samples. M.B., P.M. and P.M.O. conducted the spin transport calculations. F.F. performed the spin Hall conductivity calculations. T.K., M.B., F.F., Y.M., M.W., I.R., P.M.O. and M.M. co-wrote the paper. All authors discussed the results and commented on the manuscript.
Competing financial interests
The authors declare no competing financial interests.
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