Perspective: Magnetic skyrmions—Overview of recent progress in an active research field

Abstract

Within a decade, the field of magnetic skyrmionics has developed from a niche prediction to a huge and active research field. Not only do magnetic skyrmions—magnetic whirls with a unique topology—reveal fundamentally new physics, but they have also risen to prominence as up-and-coming candidates for next-generation high-density efficient information encoding. Within a few years, it has been possible to efficiently create, manipulate, and destroy nanometer-size skyrmions in device-compatible materials at room-temperature by all electrical means. Despite the incredibly rapid progress, several challenges still remain to obtain fully functional and competitive skyrmion devices, as discussed in this perspective article with a focus on recent results.

Skyrmion dynamics and topological sorting on periodic obstacle arrays

“…The locking can be harnessed for applications such as the sorting of different species of particles which have different sizes, charges, or damping, where a spatial separation of the species is achieved over time when one species locks to one angle while the other species locks to a different angle [26][27][28][29][30][31][32]. Up to this point, directional locking effects have been studied solely in overdamped systems where the transitions between directionally locked states can only occur when the direction of the drive with respect to the substrate symmetry is changed.Skyrmions in chiral magnets are another type of particle-like system with distinctive properties [33][34][35][36]. Magnetic skyrmions have been found in a wide variety of materials with skyrmion sizes ranging from a micron down to 10 nm, and in a number of materials, the skyrmions are stable at room temperature [37,38].…”

“…The capability to precisely control the direction, traversal distance, and reversibility of skyrmion motion could open up new ways to create such devices, and there are already a number of proposals for controlling skyrmion motion using structured substrates such as race tracks [49,51,52], periodic modulations [53], or specially designed pinning structures [54][55][56][57][58]. One proposal for controlling skyrmion motion involves having the skyrmions interact with a two dimensional periodic substrate of the type that has already been realized for colloidal particles and vortices in type-II superconductors, and there are existing experimental realizations of skyrmions interacting with two-dimensional (2D) anti-dot arrays [59].A key feature that distinguishes skyrmions from colloids and superconducting vortices is the strong non-dissipative Magnus component in the skyrmion dynamics caused by topology [34,36,60]. This affects both how the skyrmions move under a drive and how they interact with a substrate potential or pinning.…”

“…This affects both how the skyrmions move under a drive and how they interact with a substrate potential or pinning. In the absence of a substrate, the skyrmion moves at an angle with respect to the drive which is known as the intrinsic skyrmion Hall angle θ int sk [34,36]. The magnitude of this angle increases as the ratio of the Magnus force to the damping term increases.…”

“…Skyrmions in chiral magnets are another type of particle-like system with distinctive properties [33][34][35][36]. Magnetic skyrmions have been found in a wide variety of materials with skyrmion sizes ranging from a micron down to 10 nm, and in a number of materials, the skyrmions are stable at room temperature [37,38].…”

“…A key feature that distinguishes skyrmions from colloids and superconducting vortices is the strong non-dissipative Magnus component in the skyrmion dynamics caused by topology [34,36,60]. This affects both how the skyrmions move under a drive and how they interact with a substrate potential or pinning.…”