Neel-type skyrmion lattice with confined orientation in the polar magnetic semiconductor GaV₄S₈

Following the early prediction of the skyrmion lattice (SkL)-a periodic array of spin vortices-it has been observed recently in various magnetic crystals mostly with chiral structure. Although non-chiral but polar crystals with C_nv symmetry were identified as ideal SkL hosts in pioneering theoretical studies, this archetype of SkL has remained experimentally unexplored. Here, we report the discovery of a SkL in the polar magnetic semiconductor GaV₄S₈ with rhombohedral (C_3v) symmetry and easy axis anisotropy. The SkL exists over an unusually broad temperature range compared with other bulk crystals and the orientation of the vortices is not controlled by the external magnetic field, but instead confined to the magnetic easy axis. Supporting theory attributes these unique features to a new Neel-type of SkL describable as a superposition of spin cycloids in contrast to the Bloch-type SkL in chiral magnets described in terms of spin helices.