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arXiv · 2607.12595

Halogen control of magnetic competition in Kitaev candidate Ru$X_3$ ($X =$ Cl, Br)

Ryuta Iwazaki·Shinnosuke Koyama·Takashi Koretsune·Shintaro Hoshino·Joji Nasu
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Abstract

The spin-orbital Mott insulators Ru$X_3$ ($X =$ Cl, Br) have attracted considerable attention as promising candidate materials for realizing a Kitaev spin liquid. In this study, we construct effective pseudospin models from multiorbital Hubbard models derived from first-principles calculations and investigate the magnetic states of RuCl$_3$ and RuBr$_3$. From the constructed effective models, we find that RuBr$_3$ has more extended Wannier orbitals and stronger interlayer exchange interactions than RuCl$_3$. These interactions enhance three-dimensional correlations, consistent with the stronger antiferromagnetic tendency experimentally inferred for RuBr$_3$. Orbital-dependent Coulomb anisotropy further reduces the energy difference between ferromagnetic and zigzag states. Our results clarify how halogen substitution controls magnetic competition in Ru$X_3$ through interlayer exchange interactions and effects of orbital-dependent Coulomb interactions.

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Ryuta Iwazaki, Shinnosuke Koyama, Takashi Koretsune, Shintaro Hoshino, Joji Nasu. 2026-07-14. Halogen control of magnetic competition in Kitaev candidate Ru$X_3$ ($X =$ Cl, Br). https://arxiv.org/abs/2607.12595

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