Skyrmions in chiral magnets

This chapter covers the fundamental theories that led to the prediction of the skyrmion phase in chiral magnets. First, the Ginzburg–Landau theory of chiral magnets is shown to include an important contribution from the Dzyaloshinskii–Moriya interaction that results in a ground state with a spiral spin configuration. This spiral spin state was predicted to undergo a phase transition to the skyrmion crystal phase under the application of a magnetic field of sufficient strength. This prediction was later realized in the A-phase of MnSi and was soon found to be an ubiquitous phase in thin-film chiral ferromagnets. In addition to the standard Ginzburg–Landau analysis, modern approaches to skyrmion crystal phase such as classical Monte Carlo simulation and CP¹ theory are discussed.