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arXiv · 2605.11106

Contrasting structural reversibility and magnetic correlations in isostructural honeycomb magnets CrCl$_3$ and $\alpha$-RuCl$_3$

Zachary Morgan·Iris Ye·Jiasen Guo·Michael A McGuire·Jiaqiang Yan
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Abstract

We report a comparative neutron single crystal diffraction study of the structural and magnetic properties of layered halides CrCl$_3$ and $\alpha$-RuCl$_3$, which host a honeycomb arrangement of transition metal ions with distinct electronic configurations and undergo a first-order structural transition between high-temperature \textit{C}2/\textit{m} and low-temperature \textit{R}$\bar{3}$. Both compounds show a step-like change in the $c$-lattice, consistent with an expected stacking rearrangement. In contrast, the in-plane lattice response is quite different: $\alpha$-RuCl$_3$ exhibits an abrupt hysteretic change across the transition accompanied by progressive crystalline degradation upon thermal cycling, whereas CrCl$_3$ shows a smooth in-plane lattice evolution and remains structurally robust. Magnetically, CrCl$_3$ orders into an A-type antiferromagnetic structure at T$_N$=14\,K and exhibits pronounced diffuse magnetic scattering extending up to about 40\,K. $\alpha$-RuCl$_3$ shows no observable magnetic diffuse scattering above its zig-zag antiferromagnetic ordering temperature T$_N$=7.6\,K. These results suggest that the contrasting structural and magnetic behaviors arise from an interplay between interlayer sliding energetics and the fundamentally different electronic configurations of the two compounds.

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Zachary Morgan, Iris Ye, Jiasen Guo, Michael A McGuire, Jiaqiang Yan. 2026-05-11. Contrasting structural reversibility and magnetic correlations in isostructural honeycomb magnets CrCl$_3$ and $\alpha$-RuCl$_3$. https://arxiv.org/abs/2605.11106

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