Magnetic materials with noncoplanar magnetic structures can show unusual physical properties driven by nontrivial topology. Topologically-active states are often multi-q structures, which are challenging to stabilize in models and to identify in materials. Here, we use inelastic neutron-scattering experiments to show that the insulating double perovskites Ba₂YRuO₆ and Ba₂LuRuO₆ host a noncoplanar 3-q structure on the face-centered cubic lattice. Quantitative analysis of our neutron-scattering data reveals that these 3-q states are stabilized by biquadratic interactions. Our study identifies double perovskites as a highly promising class of materials to realize topological magnetism, elucidates the stabilization mechanism of the 3-q state in these materials, and establishes neutron spectroscopy on powder samples as a valuable technique to distinguish multi-q from single-q states, facilitating the discovery of topologically-nontrivial magnetic materials.

具有非共面磁性结构的磁性材料可以表现出由非平凡拓扑驱动的不寻常的物理特性。拓扑活性态通常是多q结构，这在模型中稳定和在材料中识别具有挑战性。在这里，我们利用非弹性中子散射实验表明，绝缘双钙钛矿 Ba ₂ YRuO ₆ 和 Ba ₂ LuRuO ₆ 主体面心立方晶格上的非共面 3-q 结构。对中子散射数据的定量分析表明，这些 3-q 态通过双二次相互作用而稳定。我们的研究将双钙钛矿确定为一类非常有前途的实现拓扑磁性的材料，阐明了这些材料中 3-q 态的稳定机制，并建立了粉末样品上的中子光谱作为区分多 q 与单 q 态的有价值的技术。 q 态，促进拓扑非平凡磁性材料的发现。