Angle-dependent thermodynamics of \(\alpha\)-RuCl\(_3\)

• Published in: arXiv.org 2021-01
• Main Authors: Bachus, S, Kaib, D A S, Jesche, A, Tsurkan, V, Loidl, A, Winter, S M, Tsirlin, A A, Valentí, R, Gegenwart, P
• Format: Article
• Language: English
• Subjects: Magnetic fields; Parameter identification; Spin liquid; Thermodynamics
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2101.07275

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.