Variation of spin–orbit coupling and related properties in skyrmionic system Mn FexGe

Abstract

We report a systematic study of the magnetic and magnetotransport properties in skyrmionic compounds Mn ${}_{1-x}$ Fe _x Ge. Helical-spin or skyrmion orders are formed in all the compositions, which allows us to study electron band-filling dependence of those periodically-winding spin textures. Magnetization characteristics reflect the variation in Dzyaloshinskii–Moriya interaction or spin–orbit coupling with chemical composition, typically as a change in the critical magnetic field. This tunable spin–orbit coupling enables control of skyrmion formation, such as its size, helicity and topology. Anomalous Hall effect in Mn ${}_{1-x}$ Fe _x Ge can also be a good measure of the strength of spin–orbit coupling. Anomalous Hall conductivity ${\sigma }_{{xy}}^{A}={S}_{H}M$ is moderately temperature-dependent, obeying the magnetization variation, except for those at low temperatures in FeGe accompanied by skew contribution. The constancy of anomalous Hall coefficient S _H against temperature manifests that the contribution from reciprocal space Berry phase induced by spin–orbit coupling is dominant in anomalous Hall conductivity. Strength of Dzyaloshinskii–Moriya interaction and anomalous Hall coefficient show a similar tendency in their band-filling dependence. Spin–orbit coupling plays a fundamental role behind both of the chiral magnetism and spin-dependent transport phenomena in this system.

Keywords

• skyrmion
• spin–orbit coupling
• B20-type compound
• Dzyaloshinskii–Moriya interaction
• anomalous Hall effect