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Spin-dependent trapping of electrons at spinterfaces

Nature Physics volume 9, pages 242–247 (2013)Cite this article

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Abstract

Hybrid ferromagnetic metal/organic interfaces—also known as spinterfaces—can exhibit highly efficient spin-filtering properties and therefore present a promising class of materials for the future development of new spintronic devices. Advancing the field depends critically on elucidating the fundamental microscopic processes that eventually determine the spin-filtering properties in such hybrid structures. Here, we study the femtosecond spin dynamics at the prototypical interface between cobalt and the metalorganic complex tris(8-hydroxyquinolinato)aluminium. To disentangle the microscopic origin of spin filtering, we optically generate a transient spin polarization in a well-defined hybrid interface state that we follow with a spin-resolved real-time pump–probe two-photon photoemission experiment. We find that the electrons are trapped at the interface in a spin-dependent manner for a surprisingly long time of the order of 0.5–1 ps. We conclude that ferromagnetic metal/organic interfaces act as spin filters because electrons are trapped in hybrid interface states by spin-dependent confining potentials.

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Figure 1: Conceptual principle of the 2PPE experiments revealing the spin-filtering properties of the hybrid interface formed by 1 ML Alq3 on Co(100).
Figure 2: Energetics of the Alq3/Co system and excitation channel of the uHIS in the 2PPE experiments.
Figure 3: Results of the 2PPE experiments.
Figure 4: Lifetimes extracted from the 2PPE measurements.

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Acknowledgements

The research leading to these results was partly financially supported by the EU project NMP3-SL-2011-263104 ‘HINTS’.

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Authors and Affiliations

  1. Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Strasse 46, 67663 Kaiserslautern, Germany

    Sabine Steil, Nicolas Großmann, Martin Laux, Andreas Ruffing, Daniel Steil, Martin Wiesenmayer, Stefan Mathias, Mirko Cinchetti & Martin Aeschlimann

  2. Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, 85721 Arizona, USA

    Oliver L. A. Monti

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Contributions

The experiments were planned and supervised by M.A., M.C. and S.S. The measurements were performed by N.G., M.L., A.R., D.S. and S.S. The data were analysed by N.G., S.S. and M.W. The authors M.A., M.C., N.G., O.L.A.M., S.M., D.S., S.S. and M.W. discussed the results. M.A., M.C., O.L.A.M., S.M. and S.S. wrote the manuscript.

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Correspondence to Mirko Cinchetti.

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Steil, S., Großmann, N., Laux, M. et al. Spin-dependent trapping of electrons at spinterfaces. Nature Phys 9, 242–247 (2013). https://doi.org/10.1038/nphys2548

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