Magnetic pyrochlore oxides exhibit various unconventional electronic phases and excitations due to geometric frustration. Recently, a collective magnetic excitation was reported in Raman spectroscopy on a pyrochlore ruthenate ${\mathrm{Nd}}_2{\mathrm{Ru}}_2{\mathrm{O}}_7$. However, its origin remains unclear as the Ru magnetic ground state has been controversial due to sample quality and inconsistent experimental interpretations. Here, we performed neutron diffraction measurements on a high-quality polycrystalline sample with a nearly absent magnetic impurity phase. Magnetic susceptibility and neutron diffraction measurements reveal an intrinsic Ru magnetic transition at around 145.6 K, whereas a controversial magnetic anomaly at around 21 K is suppressed in our sample, indicating that the latter is dominantly from the magnetic impurity phase. Below 145.6 K, well-defined magnetic Bragg peaks from Ru moments were observed, implying well-formed spin-spin correlations. Magnetic refinements combined with magnetic space group analysis revealed competing Ru magnetic structures, supported by density functional theory calculations. Our results suggest that the collective Raman signal may arise from competing Ru magnetic orders. Order-by-disorder and energetic scenarios are discussed as selection mechanisms for the Ru magnetic ground state. This study provides crucial insights into the search for possible order-by-disorder and topological magnetic properties in a less-studied spin-1 pyrochlore.

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• Frustrated magnetism
• Magnetic phase transitions
• Magnetic susceptibility
• Magnetism
• Antiferromagnets
• Pyrochlores
• DFT+U
• First-principles calculations
• Neutron diffraction
• Neutron scattering
• X-ray powder diffraction