Figure 46.

Devices based on current-induced motion of skyrmions in 2D magnets. (a) Skyrmion motion induced by current pulses in a FGT track.²⁶ Each STXM image is acquired after injecting five unipolar current pulses of 50 ns. Two individual Néel skyrmions are outlined in colored circled for clarity. The diameter of the skyrmions is about 200 nm, their velocity is around 1 m/s for a current density of 1.4 × 10¹¹ A/m² and the width of the track is 50 μm.²⁶ Adapted with permission from ref (26). Copyright 2021 American Physical Society. (b) Schematic of racetrack memory storing data by aligning skyrmions like beads on an abacus and displacing them by current-induced SOT from write head to read head.⁴⁷⁶ Adapted with permission from ref (476). Copyright 2018 AIP Publishing. (c) Proposal of skyrmion-based racetrack memory based on the SOT-induced motion of antiferromagnetically-coupled skyrmions in two layers coupled by AF interactions.⁵¹³ The left inset is a schematic of an antiferromagnetic (AFM or AF)-coupled nanotrack and the right inset represents AF-coupled skyrmions in Co/Ru/Co trilayers.⁵¹² As the AF-coupled skyrmions have the same chirality but opposite polarities, their motion has the advantage of being along the current direction (no Skyrmion Hall effect^509,512,513). Note that the racetrack memory of the schematic includes not only injector and detector but also an update/delete/insert. Adapted with permission from ref (513). Copyright 2018 IEEE. (d) AF-coupled CrI₃ layers in a CrI₃ bilayer.⁹ Adapted with permission from ref (9). Copyright 2018 Springer Nature.