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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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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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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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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DOI: https://doi.org/10.1038/nmat3076
