A magnon band analysis of GdRu₂Si₂ in the field-polarized state

Understanding the formation of skyrmions in centrosymmetric materials is a problem of fundamental and technological interest. GdRu₂Si₂ is a candidate material that hosts a variety of multi-Q magnetic phases, including in zero-field [1]. Here, inelastic neutron scattering is used to measure the spin excitations in the field-polarized phase of GdRu₂Si₂. Linear spin wave theory and a method of interaction invariant path analysis are used to derive a Hamiltonian accounting for the spectra. The Hamiltonian, dominated by bilinear (Ruderman-Kittel-Kasuya-Yosida) Heisenberg exchange, compares favorably to ab initio calculations. Dipolar interactions are a secondary energy scale to consider, with J_D.D~ 0.05J_RKKY. However, it is shown that in the field-polarized phase the dipolar interactions ‘self screen’ so that their effect is largely suppressed. No specific evidence for higher-order exchange is found. These aspects are discussed in the context of the lower field multi-Q states and the anisotropy of the system [2].