Magnetic field-induced chiral soliton lattice in the bulk magnetoelectric helimagnet Cu${}_2$OSeO${}_3$

Chiral soliton lattices (CSLs) are anharmonic magnetic structures typically found in uniaxial chiral magnets. In this study, we report the observation of CSL in bulk Cu${}_2$OSeO${}_3$, a chiral insulator known for its magnetoelectric properties. Using small-angle neutron scattering (SANS) experiments, we demonstrate the formation of CSLs in Cu${}_2$OSeO${}_3$ at low temperatures, driven by the competition between cubic anisotropy and magnetic field. Our observations of higher harmonics in the SANS signal clearly indicate the anharmonic nature of the spiral. This finding underscores the complex interplay between magnetic interactions in Cu${}_2$OSeO${}_3$, offering insights for potential applications of CSLs in electric-field controlled spintronic devices.