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arXiv · 2603.08237

Magnetic phase diagram and spin Hamiltonian of antiferromagnet Cs$_2$CoI$_4$

S. D. Nabi·L. Facheris·V. Romerio·V. Kocsis·K. Yu. Povarov·D. Sheptyakov·J. Lass·D. G. Mazzone·H. Kikuchi·T. Masuda·S. A. Barnett·D. R. Allan·Z. Yan·S. Gvasaliya·A. Zheludev
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Abstract

We report comprehensive thermodynamic and neutron scattering measurements on the $S$ = 3/2 antiferromagnet Cs$_2$CoI$_4$, a member of the thoroughly studied family of frustrated magnets Cs$_2MX_4$ ($M$ = Cu, Co, Ru, $X$ = Br, Cl, I, O). Unlike previously studied members, Cs$_2$CoI$_4$ undergoes a structural phase transition, for which we determine the low-temperature crystallographic structure. The resulting symmetry reduction strongly affects both the magnetic exchange interactions and single-ion anisotropy. Despite the large parameter space, we propose a minimal magnetic Hamiltonian that reasonably captures the observed excitation spectrum, analyzed using extended SU(4) linear spin-wave theory.

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S. D. Nabi, L. Facheris, V. Romerio, V. Kocsis, K. Yu. Povarov, D. Sheptyakov, J. Lass, D. G. Mazzone, H. Kikuchi, T. Masuda, S. A. Barnett, D. R. Allan, Z. Yan, S. Gvasaliya, A. Zheludev. 2026-03-09. Magnetic phase diagram and spin Hamiltonian of antiferromagnet Cs$_2$CoI$_4$. https://doi.org/10.1103/4ysh-jn8d

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