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arXiv · 2101.07275

Angle-dependent thermodynamics of $\alpha$-RuCl$_3$

S. Bachus·D. A. S. Kaib·A. Jesche·V. Tsurkan·A. Loidl·S. M. Winter·A. A. Tsirlin·R. Valentí·P. Gegenwart
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Abstract

Thermodynamics of the Kitaev honeycomb magnet $\alpha$-RuCl$_3$ is studied for different directions of in-plane magnetic field using measurements of the magnetic Gr\"uneisen parameter $\Gamma_B$ and specific heat $C$. We identify two critical fields $B_c^{\rm AF1}$ and $B_c^{\rm AF2}$ corresponding, respectively, to a transition between two magnetically ordered states and the loss of magnetic order toward a quantum paramagnetic state. The $B_c^{AF2}$ phase boundary reveals a narrow region of magnetic fields where inverse melting of the ordered phase may occur. No additional transitions are detected above $B_c^{\rm AF2}$ for any direction of the in-plane field, although a shoulder anomaly in $\Gamma_B$ is observed systematically at $8-10$ T. Large field-induced entropy effects imply additional low-energy excitations at low fields and/or strongly field-dependent phonon entropies. Our results establish universal features of $\alpha$-RuCl$_3$ in high magnetic fields and challenge the presence of a field-induced Kitaev spin liquid in this material.

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S. Bachus, D. A. S. Kaib, A. Jesche, V. Tsurkan, A. Loidl, S. M. Winter, A. A. Tsirlin, R. Valentí, P. Gegenwart. 2021-01-18. Angle-dependent thermodynamics of $\alpha$-RuCl$_3$. https://doi.org/10.1103/physrevb.103.054440

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