Advances in Magnetic Domain Walls and Their Applications

Abstract

This article explores the recent developments in spin-based domain wall (DW) memories. The physics behind the DW motion, device materials, current challenges, and applications have been discussed in detail. DWs can propagate through a magnetic nanowire by the application of external magnetic fields or by spin-polarized electric currents. Great progress has been made in these devices since the introduction of electric current-induced DW motion. However, driving DWs necessitates large spin-current densities that are incompatible with low-power devices. Therefore, significant efforts have been made to achieve highly efficient and controlled DW motion by material engineering and different mechanisms such as spin-orbit-torque (SOT), Dzyaloshinskii-Moriya interaction (DMI), and voltage-controlled magnetic anisotropy. The controlled manipulation of DWs in magnetic materials has inspired numerous strategies for high-density memory and energy-efficient logic implementation. Moreover, these devices are the potential candidates for neuromorphic computing applications that can be combined with logic-in-memory. The displacement of the DW can achieve multiple resistance states that have opened up possibilities of building artificial neurons and synapses. Despite the rapid progress, DW devices face several challenges such as low read margin, low speed, and sub-20nm scalability. Future research directions have to focus on material engineering and fabrication techniques to address these issues. Simultaneously, efforts from the circuit and system perspectives are extensively required in exploring the possible uses of these devices.