Skyrmions

Skyrmions are nanoscale spin configurations in magnetic materials that form whirling, topologically nontrivial textures. In a magnetic skyrmion the local magnetization covers the unit sphere, giving an integer topological charge that provides stability against smooth perturbations.

Most skyrmions are stabilized by a balance of exchange interactions, magnetic anisotropy, dipolar forces, and the Dzyaloshinskii-Moriya interaction or interfacial chiral effects. They occur in non-centrosymmetric bulk magnets and in thin-film multilayers where inversion symmetry is broken. External magnetic fields and temperature influence their size, density, and whether they appear as isolated particles or as lattices.

In films and some bulk materials, skyrmions range from a few to several hundred nanometers in diameter. They can form ordered lattices or exist as individual excitations. Their dynamics can be driven by electric currents through spin-transfer or spin-orbit torques, often with lower depinning currents than conventional domain walls. The topology also leads to a characteristic skyrmion Hall effect and is frequently described by collective models such as the Thiele equation.

Imaging and detection techniques include Lorentz transmission electron microscopy, spin-polarized scanning tunneling microscopy, magnetic force microscopy, and X-ray magnetic circular dichroism. These methods reveal both isolated skyrmions and skyrmion lattices in materials ranging from bulk chiral magnets like MnSi and FeGe to engineered multilayers and ferrimagnets.

Historically, skyrmions were proposed by Tony Skyrme in 1962 as a field theory model, and their condensed-matter realization was demonstrated around 2009–2010 in MnSi, with room-temperature demonstrations in various thin-film systems in the following years. Research continues toward practical applications in high-density data storage and neuromorphic computing, while challenges remain in reliable creation, control, and integration into devices.