Fast current-induced domain-wall motion controlled by the Rashba effect

Abstract

The propagation of magnetic domain walls induced by spin-polarized currents1,2,3,4,5 has launched new concepts for memory and logic devices6,7,8. A wave of studies focusing on permalloy (NiFe) nanowires9 has found evidence for high domain-wall velocities (100 m s−1; refs 10, 11), but has also exposed the drawbacks of this phenomenon for applications. Often the domain-wall displacements are not reproducible12, their depinning from a thermally stable position is difficult13 and the domain-wall structural instability (Walker breakdown14,15) limits the maximum velocity10. Here, we show that the combined action of spin-transfer and spin–orbit torques offers a comprehensive solution to these problems. In an ultrathin Co nanowire, integrated in a trilayer with structural inversion asymmetry (SIA), the high spin-torque efficiency16 facilitates the depinning and leads to high mobility, while the SIA-mediated Rashba field17,18,19 controlling the domain-wall chirality stabilizes the Bloch domain-wall structure. Thus, the high-mobility regime is extended to higher current densities, allowing domain-wall velocities up to 400 m s−1.

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Figure 1: Effects of magnetic field and electric current on domain walls.
Figure 2: Current-induced domain-wall displacements observed by Kerr microscopy.
Figure 3: Domain-wall velocity induced by current or field in the PtCoAlOx layers.
Figure 4: Domain-wall chirality reversal induced by HR .

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Acknowledgements

We thank P. Gambardella for critically reading the manuscript and useful discussions. This work was partially supported by the ANR-07-NANO-034 ‘Dynawall’ project and ERC (StG 203239). Samples were patterned at the NANOFAB facility of the Institut Néel (CNRS). The micromagnetic simulations were carried out using the Gilbert–Landau Fast Fourier Transform code initially developed by J.C. Toussaint.

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I.M.M., T.M., A.S. and G.G. designed the experiment; I.M.M., G.G., S.A. and B.R. fabricated the samples. I.M.M. and T.M. carried out the experiments assisted by S.P., J.V., M.B. and G.G; I.M.M., T.M. and G.G analysed the data and wrote the manuscript; H.S. and L.D.B-P. carried out the micromagnetic simulations. All authors discussed the results and commented on the manuscript.

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Correspondence to Ioan Mihai Miron.

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The authors declare no competing financial interests.

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Miron, I., Moore, T., Szambolics, H. et al. Fast current-induced domain-wall motion controlled by the Rashba effect. Nature Mater 10, 419–423 (2011). https://doi.org/10.1038/nmat3020

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