Figure 1

Schematic pictures of the SkXs and the crystal structure. (a–c) SkXs characterized by three spiral and sinusoidal waves along the \({\varvec{Q}}_1\), \({\varvec{Q}}_2\), and \({\varvec{Q}}_3\) directions: (a) the \(n_{\mathrm{sk}}=1\) SkX for \(\psi _\eta =0\) , (b) the \(n_{\mathrm{sk}}=2\) SkX for \(\psi _\eta =\pi /2\), and (c) the \(n_{\mathrm{sk}}=1\) T-SkX for \(\psi _\eta =\pi /6\) in Eq. (1). (d) Centrosymmetric trigonal structure without the horizontal mirror plane. The blue spheres represent magnetic sites, while the gray spheres shifted by \(+ c\) (\(-c\)) from the center of the downward (upward) triangles on the magnetic layer represent nonmagnetic sites on a layer A (B).