Possible higher-order skyrmion crystal in S = 1 van der Waals Kitaev triangular antiferromagnet NiI₂

Topological spin textures, such as magnetic skyrmions, represent a promising platform for spintronics applications. However, most known skyrmion candidates are limited to a topological number of one and are typically stabilized within a narrow range of temperature and magnetic field. Recent theoretical work has proposed that a higher-order skyrmion crystal phase—characterized by a crystallized spin texture with a topological number greater than one—may be achievable through the Kitaev interaction in the triangular antiferromagnet NiI₂. Here, using neutron scattering and simulations, we demonstrate that the magnetic insulator NiI₂ can possibly exhibit a skyrmion crystal phase with a topological number of two (SkX-2 phase) at intermediate temperatures (60K–75K). We identified a significant antiferromagnetic Kitaev interaction from magnetic diffuse scattering in NiI₂. Furthermore, our optimized parameter set stabilizes this higher-order skyrmion crystal phase, which can be connected with the intermediate-temperature phase observed in bulk samples. These findings highlight new avenues for spintronic devices leveraging higher-order skyrmion crystals and van der Waals magnets