Variation of spin-orbit coupling and related properties in skyrmionic system Mn1-xFexGe

We report a systematic study of the magnetic and magnetotransport properties in skyrmionic compounds Mn1-xFexGe. 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 Mn1-xFexGe can also be a good measure of the strength of spin-orbit coupling. Anomalous Hall conductivity sigma(A)(xy) = SHM 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.