Ruthenium trihalides $\mathrm{Ru}{X}_3$ ($X=\text{Cl,}\text{Br,}\text{I}$) provide a tunable platform for Kitaev magnetism in two-dimensional van der Waals materials. Despite their similar crystal structures and zigzag antiferromagnetic order, ${\mathrm{RuBr}}_3$ exhibits a higher Néel temperature ($T_N$) than ${\mathrm{RuCl}}_3$, suggesting their distinct proximity to the Kitaev quantum spin-liquid phase. Using Ru $L_3$-edge resonant x-ray scattering, we show that, while the long-range zigzag order in ${\mathrm{RuBr}}_3$ disappears at $T_N$, the zigzag correlations that persist well above $T_N$ show a pronounced spectral weight redistribution along the interlayer direction. These results suggest that the enhanced interlayer magnetic interactions driven by the extended Br $4p$ orbitals stabilize three-dimensional zigzag correlations in ${\mathrm{RuBr}}_3$.

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• Magnetism
• Strongly correlated systems
• Resonant inelastic x-ray scattering