Domain walls (DW) in synthetic anti-ferromagnetic and synthetic ferrimagnetic (SyF) tracks can be driven efficiently with low current densities. Experimental results on DW motion in SyF tracks have been modelled using Boris, as detailed in S. Lepadatu et al., “Synthetic ferrimagnet nanowires with very low critical current density for coupled domain wall motion” Scientific Reports 7, 1640 (2017).

Domain walls in synthetic ferrimagnet nanostructures, showing a) Diagram of SyF track indicating the directions of magnetisation, x-ray beam in the PEEM, electron flow during magnetotransport, and applied field (H). b) High-resolution TEM cross-section of SyF thin film. The layers are t1 = 13:3 nm and t2 = 6:6 nm thick separated by a 0:7 nm thick Ru spacer layer. c) XMCD-PEEM images and micromagnetic simulations of SyF structure with 400 nm wide track, showing reversal of ellipse and track in the thicker Co90Fe10 layer. XMCD-PEEM images are taken at remanence after application of a field pulse. The color wheel indicates the magnetisation directions in the thicker layer, in the micromagnetic simulations. d) LTEM image of injected DW in SyF track with 800 nm width. The measured DW width is ~ 100 nm. The red and blue arrows indicate the inferred direction of magnetisation in the two layers.

The measured current-driven velocity is shown below, both for AFM (SyF) and FM coupled layers, showing threshold current density as low as ~1011 A/m2

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