Prioritization of the influence of different exchange interactions and uniaxial anisotropy on the generation and morphology of skyrmions

Abstract

Different magnetic interactions and anisotropy in the multi-layer structure have different effects on the formation and morphology of skyrmions under zero field. In this paper, we show that the Ruderman–Kittel–Kasuya–Yosida (RKKY) coupling plays a dominant role in the generation of skyrmions but has no significant effect on the size of skyrmions. When the RKKY coupling is weak, if the Dzyaloshinskii–Moriya interaction (DMI) is strong enough, some irregular cruciform domain states can be formed. With the increase of the DMI, the shape of skyrmions is altered from Néel skyrmions to skyrmioniums, and when the Heisenberg exchange is relatively low, complex domain states, such as the labyrinth are formed. However, when the Heisenberg coupling is comparatively high, the spin states of the Néel-skyrmions are reversed. Both the Heisenberg exchange interaction and uniaxial anisotropy have a positive influence on reducing the diameters of skyrmions. However, skyrmions are difficult to generate when the Heisenberg exchange and anisotropy are strong enough. We find the prioritization of the effects of different magnetic interactions and uniaxial anisotropy on the formation and morphology of skyrmions by analyzing the energy diagrams, combined with the magnetization configuration in different pairs of the exchange interactions and anisotropy, in which the RKKY coupling has the greatest influence, followed by the DMI, then the Heisenberg exchange and finally the uniaxial anisotropy.