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Seebeck effect in magnetic tunnel junctions

Nature Materials volume 10, pages 742–746 (2011)Cite this article

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Abstract

Creating temperature gradients in magnetic nanostructures has resulted in a new research direction, that is, the combination of magneto- and thermoelectric effects1,2,3,4,5. Here, we demonstrate the observation of one important effect of this class: the magneto-Seebeck effect. It is observed when a magnetic configuration changes the charge-based Seebeck coefficient. In particular, the Seebeck coefficient changes during the transition from a parallel to an antiparallel magnetic configuration in a tunnel junction. In this respect, it is the analogue to the tunnelling magnetoresistance. The Seebeck coefficients in parallel and antiparallel configurations are of the order of the voltages known from the charge–Seebeck effect. The size and sign of the effect can be controlled by the composition of the electrodes’ atomic layers adjacent to the barrier and the temperature. The geometric centre of the electronic density of states relative to the Fermi level determines the size of the Seebeck effect. Experimentally, we realized 8.8% magneto-Seebeck effect, which results from a voltage change of about −8.7 μV K−1 from the antiparallel to the parallel direction close to the predicted value of −12.1 μV K−1. In contrast to the spin–Seebeck effect, it can be measured as a voltage change directly without conversion of a spin current.

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Figure 1: Origin of the magneto-Seebeck effect.
Figure 2: Switching of the Seebeck effect through the magnetization.
Figure 3: Cross-sections and temperature gradients in the tunnel junction.
Figure 4: Seebeck voltages for Fe–Co–B/MgO/Fe–Co–B elements.

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Acknowledgements

A.T. acknowledges the Ministry of Innovation, Science and Research of the North Rhine-Westphalia state government for financial support. M.M., M.S., M.W. and P.P. acknowledge the funding provided by the German Research Foundation through the SFB 602 for the TEM work. M.C., M.B. and C.H. acknowledge support from German Research Foundation SPP 1386 and German Research Foundation grant HE 5922/1-1. J.S.M acknowledges support by the US National Science Foundation and Office of Naval Research. We acknowledge A. Zeghuzi’s help for extra COMSOL calculations. This work was initiated by the SpinCaT priority program.

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Authors and Affiliations

  1. I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany

    Marvin Walter, Jakob Walowski, Vladyslav Zbarsky & Markus Münzenberg

  2. Department of Physics, Universität Bielefeld, 33501 Bielefeld, Germany

    Markus Schäfers, Daniel Ebke, Günter Reiss & Andy Thomas

  3. Institut für angewandte Physik, Universität Hamburg, 20355 Hamburg, Germany

    Andy Thomas

  4. IV. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany

    Patrick Peretzki & Michael Seibt

  5. Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

    Jagadeesh S. Moodera

  6. I. Physikalisches Institut, Justus-Liebig-Universität Gießen, 35392 Gießen, Germany

    Michael Czerner, Michael Bachmann & Christian Heiliger

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  1. Marvin Walter
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Contributions

M.W. and J.W. carried out experiments; M.W., V.Z., M.Sch. and D.E. characterized and prepared the TMR devices; P.P. and M.S. carried out the high-resolution TEM; M.W., J.W. and M.M. analysed the data; M.W. carried out the COMSOL calculations; M.C., M.B. and C.H. did the ab initio transport calculations; A.T. and M.M. designed the research approach; C.H., M.M. and A.T. wrote the manuscript and developed the model; M.W., J.S.M., A.T., M.M. and C.H. contributed to the development of the experiments; G.R., J.S.M., A.T., M.M., C.H. and all authors discussed the experiments and the manuscript.

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Correspondence to Markus Münzenberg.

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The authors declare no competing financial interests.

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Walter, M., Walowski, J., Zbarsky, V. et al. Seebeck effect in magnetic tunnel junctions. Nature Mater 10, 742–746 (2011). https://doi.org/10.1038/nmat3076

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