  Skyrmion stabilization in novel magnetic systems with the B20 crystal
structure is reported here, primarily based on theoretical results. The focus
is on the effect of alloying on the 3d sublattice of the B20 structure by
substitution of heavier 4d and 5d elements, with the ambition to tune the
spin-orbit coupling and its influence on magnetic interactions.
State-of-the-art methods based on density functional theory are used to
calculate both isotropic and anisotropic exchange interactions. Significant
enhancement of the Dzyaloshinskii-Moriya interaction is reported for 5d-doped
FeSi and CoSi, accompanied by a large modification of the spin stiffness and
spiralization. Micromagnetic simulations coupled to atomistic spin-dynamics and
ab initio magnetic interactions reveal a helical ground state and field-induced
skyrmions for all these systems. Especially small skyrmions $\sim$50 nm are
predicted for Co$_{0.75}$Os$_{0.25}$Si, compared to $\sim$148 nm for
Fe$_{0.75}$Co$_{0.25}$Si. Convex-hull analysis suggests that all B20 compounds
considered here are structurally stable at elevated temperatures and should be
possible to synthesize. This prediction is confirmed experimentally by
synthesis and structural analysis of the Ru-doped CoSi systems discussed here,
both in powder and in single-crystal forms.
