Spatially and time-resolved magnetization dynamics driven by spin–orbit torques

Abstract

Current-induced spin–orbit torques are one of the most effective ways to manipulate the magnetization in spintronic devices, and hold promise for fast switching applications in non-volatile memory and logic units. Here, we report the direct observation of spin–orbit-torque-driven magnetization dynamics in Pt/Co/AlOx dots during current pulse injection. Time-resolved X-ray images with 25 nm spatial and 100 ps temporal resolution reveal that switching is achieved within the duration of a subnanosecond current pulse by the fast nucleation of an inverted domain at the edge of the dot and propagation of a tilted domain wall across the dot. The nucleation point is deterministic and alternates between the four dot quadrants depending on the sign of the magnetization, current and external field. Our measurements reveal how the magnetic symmetry is broken by the concerted action of the damping-like and field-like spin–orbit torques and the Dzyaloshinskii–Moriya interaction, and show that reproducible switching events can be obtained for over 1012 reversal cycles.

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Figure 1: Schematic of the experimental set-up and sample structure.
Figure 2: Time-resolved magnetization switching.
Figure 3: Evolution of the magnetization during the switching process.
Figure 4: Effect of an external field balancing the field-like torque.
Figure 5: Micromagnetic simulations of the reversal process.
Figure 6: Partial switching induced by subthreshold current pulses.

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Acknowledgements

This work was funded by the Swiss National Science Foundation (grant numbers 200021-153404 and 200020-172775). Part of this work was performed at the PolLux (X07DA) endstation of the Swiss Light Source, Villigen, Switzerland. The PolLux end station was financed by the German Minister für Bildung und Forschung (BMBF) through contracts 05KS4WE1/6 and 05KS7WE1. We acknowledge fruitful discussions with J. Stöhr and L. Buda-Prejbeanu.

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M.B., K.G. and P.G. planned the experiments and analysed the data. M.B., M.G. and J.F. fabricated the samples. M.B., K.G., J.M., C.O.A., E.G., C.M., C.S., Y.A., S.F., S.W. and J.R. implemented the current pump/X-ray probe scheme and performed the scanning transmission X-ray microscopy experiments. M.B. carried out the electrical measurements and the micromagnetic simulations. M.B. and P.G. wrote the manuscript. All authors discussed the data and commented on the manuscript.

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Correspondence to Manuel Baumgartner or Kevin Garello or Pietro Gambardella.

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The authors declare no competing financial interests.

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Baumgartner, M., Garello, K., Mendil, J. et al. Spatially and time-resolved magnetization dynamics driven by spin–orbit torques. Nature Nanotech 12, 980–986 (2017). https://doi.org/10.1038/nnano.2017.151

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