The Spatial Resolution Limit for Domain Walls in Sub-100-nm-wide Magnetic Nanowires
Magnetic nanowires are the foundation of several promising nonvolatile computing devices, most notably racetrack memory and domain wall logic. Here, we determine the analog information capacity in these technologies, analyzing a magnetic nanowire containing a single domain wall. Magnetic domain walls are characterized by their wall energy, and relax into minima in the energy landscape of the wire. When the width of a magnetic nanowire decreases below 100 nm, domain walls are increasingly influenced by inhomogeneities at the edges of the wire that affect the energy landscape. Indeed, wires can be deliberately patterned with notches to define discrete positions for domain walls. However, at dimensions below the resolution of the fabrication process, the line edge roughness of the wire can also trap domain walls, setting the fundamental resolution limit for the placement of a domain wall. The spatial resolution limit that we determine for a single domain wall positioned along the length of a nanowire shows how the nanowire fabrication process ultimately limits the information capacity and scalability of nonvolatile domain wall devices.