Engineering Dzyaloshinskii-Moriya interaction in B20 thin-film chiral magnets

Chiral magnetic $\mathrm{M}{\mathrm{n}}_x\mathrm{F}{\mathrm{e}}_{1\ensuremath{-}x}\mathrm{Ge}$ compounds have an antisymmetric exchange interaction that is tunable with the manganese stoichiometric fraction, $x$. Although millimeter-scale, polycrystalline bulk samples of this family of compounds have been produced, thin-film versions of these materials will be necessary for devices. In this study, we demonstrate the growth of epitaxial $\mathrm{M}{\mathrm{n}}_x\mathrm{F}{\mathrm{e}}_{1\ensuremath{-}x}\mathrm{Ge}$ thin films on Si(111) substrates with a pure B20 crystal structure in the stoichiometric fraction range $x$ from 0 to 0.81. Following systematic structural analysis and magnetic characterization consisting of dc magnetization measurements and microwave absorption spectroscopy, we quantify the antisymmetric exchange interaction and helical period as a function of $x$, which ranges from 200 nm to 8 nm. Our results demonstrate an approach to engineering the size of magnetic skyrmions in epitaxial films that are grown using scalable techniques.