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The centrosymmetric material Gd₂PdSi₃ may host a skyrmion phase under applied magnetic field [1,2]. Unusually, this proposed state is stabilized by frustrated interactions within triangular Gd³⁺ planes, rather than by antisymmetric interactions. However, neither the zero-field magnetic structure nor the underlying spin Hamiltonian of Gd₂PdSi₃ has been conclusively determined [3,4]. Here, we present neutron diffraction and spectroscopy measurements on an isotopically-enriched polycrystalline Gd₂PdSi₃ sample. Our analysis of magnetic diffuse and inelastic scattering data indicates substantial ferromagnetic inter-planar coupling, and spatially-extended interactions in triangular planes, likely consistent with an RKKY mechanism [5]. Our Rietveld refinements show that the ordered magnetic moments lie perpendicular to the magnetic propagation vector, k ~ (0.15,0,0), and constrain candidate magnetic structures. We discuss our neutron data in the context of theoretical and experimental studies of candidate spin-texture materials.

[1] Kurumaji et al., Science 365, 914 (2019); [2] Mallik et al., EPL 41, 315 (1998); [3] Moody et al., arXiv:2010.14326v1 (2020); [4] Nomoto et al., Phys. Rev. Lett. 125, 117204 (2020); [5] Wang et al., Phys. Rev. Lett. 124, 207201 (2020).