Spin–orbit torque magnetization switching controlled by geometry

Abstract

Magnetization reversal by an electric current1,2,3,4,5,6,7,8,9 is essential for future magnetic data storage technology1, such as magnetic random access memories4. Typically, an electric current is injected into a pillar-shaped magnetic element, and switching relies on the transfer of spin momentum1,2,3,4 from a ferromagnetic reference layer (an approach known as spin–transfer torque). Recently, an alternative technique has emerged that uses spin–orbit torque (SOT) and allows the magnetization to be reversed without a polarizing layer by transferring angular momentum directly from the crystal lattice5,6,7,8,9. With spin–orbit torque, the current is no longer applied perpendicularly, but is in the plane of the magnetic thin film. Therefore, the current flow is no longer restricted to a single direction and can have any orientation within the film plane. Here, we use Kerr microscopy to examine spin–orbit torque-driven domain wall motion in Co/AlOx wires with different shapes and orientations on top of a current-carrying Pt layer. The displacement of the domain walls is found to be highly dependent on the angle between the direction of the current and domain wall motion, and asymmetric and nonlinear with respect to the current polarity. Using these insights, devices are fabricated in which magnetization switching is determined entirely by the geometry of the device.

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Figure 1: The geometric specificity of SOT with respect to STT.
Figure 2: Non-collinear domain wall motion.
Figure 3: Device geometry design.
Figure 4: Geometric magnetization reversal.

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Acknowledgements

This work was supported by the European Commission under the Seventh Framework Programme (grant nos. 318144, 2012-322369) and French Government Project ANR-11-BS10-0008. The devices were fabricated at Nanofab CNRS and the Plateforme de Technologique Amont in Grenoble.

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C.K.S., E.J., G.G. and I.M.M. planned the experiment. I.M.M., G.G., A.L. and S.A. fabricated the samples. C.K.S., E.J., S.P. and I.M.M. performed the experiments. C.K.S. and I.M.M. analysed the data and wrote the manuscript. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Ioan Mihai Miron.

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The authors declare no competing financial interests.

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Safeer, C., Jué, E., Lopez, A. et al. Spin–orbit torque magnetization switching controlled by geometry. Nature Nanotech 11, 143–146 (2016). https://doi.org/10.1038/nnano.2015.252

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