A thermodynamic reference for field-induced phenomena in α-RuCl3: two coexisting polymorphs account for multiple magnetic phase transitions
Abstract
The majority of research on α-RuCl3 has focused on applying in-plane magnetic fields to suppress the antiferromagnetic order and induce a quantum spin liquid (QSL). However, interpreting field-induced phenomena has been complicated by the material's temperature- and sample-size-dependent crystal structure and its sensitivity to strain-induced stacking disorder. Here, we isolate the monoclinic (C2/m) phase in nanogram-scale single crystals, providing the opportunity to study Kitaev physics in a new setting. We perform high-resolution magnetotropic susceptibility measurements on a structurally well-defined crystal within several crystal planes. Mapping the antiferromagnetic (AFM) phase boundary as a function of temperature, magnetic field, and field orientation, we find that the monoclinic phase diagram closely resembles that of rhombohedral crystals, but is systematically shifted to higher transition temperatures and critical fields. We find that the critical fields coincide quantitatively with anomalies observed across the ∼7-11~T field range, where Kitaev spin liquid physics has been widely reported across numerous independent studies and experimental techniques. Our study shows that these anomalies arise from the magnetic phase boundaries of coexisting monoclinic and rhombohedral structural domains, rather than an exotic phase. These results provide a thermodynamic reference against which past studies can determine their structural composition, and toward which future studies can look for genuine signatures of spin-liquid phenomena beyond the close vicinity of the AFM boundary under in-
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BibTeX
@misc{nasir2026thermodynamic,
title = {{A thermodynamic reference for field-induced phenomena in $α$-RuCl$_3$: two coexisting polymorphs account for multiple magnetic phase transitions}},
author = {Hamza Nasir and Daniel Balazs and Muhammad Nauman and Vikram Nagarajan and Ezekiel Horsley and Subin Kim and Young-June Kim and K. A. Modic},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2605.13444},
eprint = {2605.13444},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.13444},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A thermodynamic reference for field-induced phenomena in α-RuCl_3: two coexisting polymorphs account for multiple magnetic phase transitions
AU - Hamza Nasir
AU - Daniel Balazs
AU - Muhammad Nauman
AU - Vikram Nagarajan
AU - Ezekiel Horsley
AU - Subin Kim
AU - Young-June Kim
AU - K. A. Modic
PY - 2026
DA - 2026/10/03
PB - arXiv
DO - 10.48550/arxiv.2605.13444
UR - https://arxiv.org/abs/2605.13444
AB - The majority of research on α-RuCl_3 has focused on applying in-plane magnetic fields to suppress the antiferromagnetic order and induce a quantum spin liquid (QSL). However, interpreting field-induced phenomena has been complicated by the material's temperature- and sample-size-dependent crystal structure and its sensitivity to strain-induced stacking disorder. Here, we isolate the monoclinic (C2/m) phase in nanogram-scale single crystals, providing the opportunity to study Kitaev physics in a new setting. We perform high-resolution magnetotropic susceptibility measurements on a structurally well-defined crystal within several crystal planes. Mapping the antiferromagnetic (AFM) phase boundary as a function of temperature, magnetic field, and field orientation, we find that the monoclinic phase diagram closely resembles that of rhombohedral crystals, but is systematically shifted to higher transition temperatures and critical fields. We find that the critical fields coincide quantitatively with anomalies observed across the ∼7-11~T field range, where Kitaev spin liquid physics has been widely reported across numerous independent studies and experimental techniques. Our study shows that these anomalies arise from the magnetic phase boundaries of coexisting monoclinic and rhombohedral structural domains, rather than an exotic phase. These results provide a thermodynamic reference against which past studies can determine their structural composition, and toward which future studies can look for genuine signatures of spin-liquid phenomena beyond the close vicinity of the AFM boundary under in-
ER -