Edge-potential induced skyrmion pinning and radial deformations under varying non-adiabatic spin torques

Abstract

Magnetic skyrmions are non-trivial topological spin textures that garnered intensive research attention due to their futuristic potential applications under their low-current-driven dynamics at the nano-length scale. Skyrmions-based racetrack memory devices where data can be embedded using skyrmions is a promising information storage technology. This makes the exploration of skyrmion transport properties on a racetrack under the influence of potential parameters is crucial for the designing of these next-generation energy-efficient memory devices. A systematic analysis of the influence of non-adiabatic spin torques and other key material parameters on skyrmion motion is presented using micromagnetic simulations. Skyrmions size-dependent dynamics in response to the edge potential under constant current density for Néel-type skyrmions are investigated. The theoretical frameworks indicate that smaller skyrmions drift off to a larger distance in the transverse direction owing to their smaller radius and smaller edge repulsion, eventually saturating with variation in their radius depending on the non-adiabatic torque coefficient. The smaller skyrmion shows undeformed stabilized states expelled at the edges with the increased difference in Gilbert damping (α) and non-adiabatic torque coefficient (β). The results also indicate a non-uniform distortion in the case of smaller skyrmions, deviating from their initial circular configuration to elliptical edge states while larger stabilized skyrmion states preserve their circular symmetry. We further discuss the influence of spin–orbit torques and interfacial spin-transfer torques on the skyrmion motion. These results provide a comprehensive understanding of the skyrmion pinning characteristics under the balancing act of Magnus force and skyrmion-edge repulsion.