Zoology of Multiple‐Q Spin Textures in a Centrosymmetric Tetragonal Magnet with Itinerant Electrons

Magnetic skyrmion is a topologically stable particle‐like swirling spin texture potentially suitable for high‐density information bit, which was first observed in noncentrosymmetric magnets with Dzyaloshinskii–Moriya interaction. Recently, nanometric skyrmion has also been discovered in centrosymmetric rare‐earth compounds, and the identification of their skyrmion formation mechanism and further search of nontrivial spin textures are highly demanded. Here, magnetic structures in a prototypical skyrmion‐hosting centrosymmetric tetragonal magnet GdRu(2)Si(2) is exhaustively studied by performing the resonant X‐ray scattering experiments. A rich variety of double‐Q magnetic structures, including the antiferroic order of meron(half‐skyrmion)/anti‐meron‐like textures with fractional local topological charges are identified. The observed intricate magnetic phase diagram is successfully reproduced by the theoretical framework considering the four‐spin interaction mediated by itinerant electrons and magnetic anisotropy. The present results will contribute to the better understanding of the novel skyrmion formation mechanism in this centrosymmetric rare‐earth compound, and suggest that itinerant electrons can ubiquitously host a variety of unique multiple‐Q spin orders in a simple crystal lattice system.