Formation of Field-Free Skyrmion Arrays in Pt/Co/Ni/Ir-based Multilayer Thin Films

Magnetic skyrmions are topologically protected spin textures which have garnered a great deal of attention in recent years for their favorable properties for nonvolatile memory and neuromorphic computing applications. The deterministic chirality of these objects are stabilized by the Dzyaloshinskii-Moriya interaction (DMI) and typically require a perpendicular magnetic field to be stabilized but often appear with fairly low densities. Here we demonstrate a simple method to form high-density skyrmion arrays at remanence following the brief application of a large in-plane magnetic field. We characterize these arrays using Lorentz transmission electron microscopy and observe that the size of the observed skyrmions are strongly influenced by the strength of interfacial DMI. We also find the angle of the applied field with respect to the film normal strongly influences the formation of arrays as opposed to labyrinthine domains. This is particularly apparent around bend contours of the TEM membrane which can have large variations in apparent tilt.