Figure 4

(a) χ′_ac vs. H plot at temperatures 50–57 K. (b) Selected temperature curves from (a), but offset each other for easy comparison. The notations of H_A1 and H_A2 indicate skyrmion phase boundaries while H_C1 and H_C2 indicate conical phase boundaries respectively. The values of H_A1 and H_A2 are determined by the peaks while H_C1 and H_C2 are the inflection points in the first derivative of χ′_ac vs. H curves. (c) H vs. T phase diagram for Cu₂OSeO₃, where the skyrmion phase zone is marked in red.