Electric-Field-Driven Switching of Individual Magnetic Skyrmions*

Based on the discovery of nanoscale magnetic skyrmion lattices [1] as well as individual skyrmions [2] in ultrathin magnetic films and bilayers, stabilized by interfacial Dzyaloshinskii-Moriya interactions, applications of magnetic skyrmions for future spintronic devices, such as memory and logic elements, have become feasible [3]. The properties of magnetic skyrmions can widely be tuned, e.g. by multiple interface engineering, leading to skyrmionic states in metallic multilayer systems being stable up to room temperature [4-6] and in zero magnetic field. Alternatively, chemical treatments, e.g. by oxidation or hydrogenation of ultrathin magnetic thin films can serve as a simple route towards tailored skyrmionic states.
By locally injecting spin-polarized electrons from an atomically sharp SP-STM tip, writing and deleting of individual skyrmions has been demonstrated, making use of spin-transfer torque exerted by the injected high-energy spin-polarized electrons [2]. Alternatively, individual skyrmions can be created and deleted by local electric fields [7], which can be of great advantage in view of energy-efficient skyrmionic device concepts. The subsequent detection of the written skyrmions can also be achieved by electrical means rather than by using a magnetic sensing element [8]. These results highlight the potential of current-driven skyrmions for future racetrack-type memory applications [3].
[1] S. Heinze et al., Nature Physics 7, 713 (2011).
[2] N. Romming et al., Science 341, 6146 (2013).
[3] R. Wiesendanger, Nature Reviews Materials 1, 16044 (2016).
[4] G. Chen et al., Appl. Phys. Lett. 106, 242404 (2015).
[5] C. Moreau-Luchaire et al., Nature Nanotechnology 11, 444 (2016).
[6] S. Woo et al., Nature Materials 15, 501 (2016).
[7] P.-J. Hsu et al., Nature Nanotechnology 12, 123 (2017).
[8] C. Hanneken et al., Nature Nanotechnology 10, 1039 (2015).