Magnetic domain wall substructures in Pt/Co/Ni/Ir multi-layers

Abstract

We examine the substructures of magnetic domain walls (DWs) in [Pt/(Co/Ni)${}_M$ /Ir]${}_N$ multi-layers using a combination of micromagnetic theory and Lorentz transmission electron microscopy. Thermal stability calculations of $\mathrm{Q}=\pm 1$ substructures [2$\pi$ vertical Bloch lines and DW skyrmions] were performed using a geodesic nudged elastic band model, which supports their metastability at room temperature. Experimental variation in strength of the interfacial Dzyaloshinskii–Moriya interaction and film thickness reveals conditions under which these substructures are present and enables the formation of a magnetic phase diagram. Reduced thickness is found to favor $\mathrm{Q}=\pm 1$ substructures likely due to the suppression of hybrid DWs. The results from this study provide an important framework for examining 1D DW substructures in chiral magnetic materials.