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arXiv · 2610.39669

High-Field Heat Capacity of Atacamite Cu$_2$Cl(OH)$_3$ for $\mathbf{H} \parallel b$ axis: From Antiferromagnetic Order to Correlated Disorder

L. Stödter·A. Demuer·T. Kotte·A. U. B. Wolter·B. Büchner·K. C. Rule·S. Süllow
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Abstract

We present the heat capacity of the frustrated sawtooth-chain compound atacamite Cu$_2$Cl(OH)$_3$ in high magnetic fields up to 35 T for $\mathbf{H} \parallel b$ axis. We clearly observe the change from antiferromagnetic long-range order, indicated by a sharp transition anomaly shifted to lower temperatures when increasing field, to a field-induced spin-liquid-like state with the absence of any transition anomaly. Here, in highest magnetic fields above 32 T a broad anomaly is present which is shifted to higher temperatures as the field is increased. The low-temperature heat capacity in the high-field region can be described well by an exponential behavior indicating a thermal activation over a spin gap. The findings are consistent with our scenario for the high-field state in atacamite for $\mathbf{H} \parallel c$ axis, where we proposed the sawtooth chains to decouple into two spin subsystems, basal and apical spin sites, leading to a partially polarized state with $M \sim M_\mathrm{sat}/2$.

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L. Stödter, A. Demuer, T. Kotte, A. U. B. Wolter, B. Büchner, K. C. Rule, S. Süllow. 2026-10-29. High-Field Heat Capacity of Atacamite Cu$_2$Cl(OH)$_3$ for $\mathbf{H} \parallel b$ axis: From Antiferromagnetic Order to Correlated Disorder. https://arxiv.org/abs/2610.39669

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