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Reversible electrical switching of spin polarization in multiferroic tunnel junctions

Abstract

Spin-polarized transport in ferromagnetic tunnel junctions, characterized by tunnel magnetoresistance1, has already been proven to have great potential for application in the field of spintronics2 and in magnetic random access memories3. Until recently, in such a junction the insulating barrier played only a passive role, namely to facilitate electron tunnelling between the ferromagnetic electrodes. However, new possibilities emerged when ferroelectric materials were used for the insulating barrier, as these possess a permanent dielectric polarization switchable between two stable states4,5,6,7,8,9. Adding to the two different magnetization alignments of the electrode, four non-volatile states are therefore possible in such multiferroic tunnel junctions10,11. Here, we show that owing to the coupling between magnetization and ferroelectric polarization at the interface between the electrode and barrier of a multiferroic tunnel junction, the spin polarization of the tunnelling electrons can be reversibly and remanently inverted by switching the ferroelectric polarization of the barrier. Selecting the spin direction of the tunnelling electrons by short electric pulses in the nanosecond range rather than by an applied magnetic field enables new possibilities for spin control in spintronic devices12.

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Figure 1: Structure and basic properties of the multiferroic tunnel junctions.
Figure 2: Tunnel electro- and magnetoresistance properties of Co/PZT(3.2 nm)/LSMO junctions.
Figure 3: Model of the influence of the ferroelectric polarization on the spin polarization.

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Acknowledgements

This work has been supported by the German Science Foundation (DFG) through SFB 762. We are grateful to N. Schammelt for technical assistance and G. Schmidt for useful discussions. We thank P. Werner for help with HRTEM.

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Contributions

D.P. and M.A. designed the experiments; D.P. carried out the experiments; S.G. and D.P. prepared the samples; S.G. carried out the TEM investigations; D.P. and M.A. analysed and discussed the results; D.P., M.A. and D.H. prepared the manuscript.

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Correspondence to M. Alexe.

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The authors declare no competing financial interests.

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Pantel, D., Goetze, S., Hesse, D. et al. Reversible electrical switching of spin polarization in multiferroic tunnel junctions. Nature Mater 11, 289–293 (2012). https://doi.org/10.1038/nmat3254

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