Crystalline water intercalation into the Kitaev honeycomb cobaltate Na$_2$Co$_2$TeO$_6$

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Main Authors: Ito, Masaaki, Haraguchi, Yuya, Motohashi, Teruki, Saito, Miwa, Ogawa, Satoshi, Ikuta, Takashi, Katori, Hiroko Aruga
Format: Preprint
Published: 2025
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author Ito, Masaaki
Haraguchi, Yuya
Motohashi, Teruki
Saito, Miwa
Ogawa, Satoshi
Ikuta, Takashi
Katori, Hiroko Aruga
author_facet Ito, Masaaki
Haraguchi, Yuya
Motohashi, Teruki
Saito, Miwa
Ogawa, Satoshi
Ikuta, Takashi
Katori, Hiroko Aruga
contents We herein report the successful intercalation of water molecules into the layered honeycomb lattice of Na$_2$Co$_2$TeO$_6$, a Kitaev-candidate compound, to obtain the hydrated phase Na$_2$Co$_2$TeO$_6$$\cdot$$y$H$_2$O ($y \sim$ 2.4). Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and Rietveld refinements indicate that crystalline water resides between the cobalt-based honeycomb layers. This insertion of neutral molecules significantly alters the crystal structure, increasing the interlayer spacing and modifying the local bonding environment. Magnetization measurements reveal an antiferromagnetic transition at $T_N \sim 17.2$ K, accompanied by a discernible weak ferromagnetic component. The application of moderate magnetic fields induces a spin-flop reorientation at $μ_0H \sim 5.7$ T. The $λ$-type anomaly and long-range order persist up to 9 T, showing the reconfiguration of the ground state as opposed to its suppression. Heat-capacity analysis reveals the full $2R\ln2$ magnetic entropy expected for two $J_{\rm eff} = 1/2$ moments per formula unit, confirming the pseudospin description. These findings demonstrate that water intercalation is a robust strategy for tuning the magnetic properties of honeycomb lattice materials. Overall, this study highlights neutral-molecule insertion as a promising route toward the discovery and engineering of quantum magnets based on layered transition metal oxides.
format Preprint
id arxiv_https___arxiv_org_abs_2508_08717
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Crystalline water intercalation into the Kitaev honeycomb cobaltate Na$_2$Co$_2$TeO$_6$
Ito, Masaaki
Haraguchi, Yuya
Motohashi, Teruki
Saito, Miwa
Ogawa, Satoshi
Ikuta, Takashi
Katori, Hiroko Aruga
Strongly Correlated Electrons
Materials Science
We herein report the successful intercalation of water molecules into the layered honeycomb lattice of Na$_2$Co$_2$TeO$_6$, a Kitaev-candidate compound, to obtain the hydrated phase Na$_2$Co$_2$TeO$_6$$\cdot$$y$H$_2$O ($y \sim$ 2.4). Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and Rietveld refinements indicate that crystalline water resides between the cobalt-based honeycomb layers. This insertion of neutral molecules significantly alters the crystal structure, increasing the interlayer spacing and modifying the local bonding environment. Magnetization measurements reveal an antiferromagnetic transition at $T_N \sim 17.2$ K, accompanied by a discernible weak ferromagnetic component. The application of moderate magnetic fields induces a spin-flop reorientation at $μ_0H \sim 5.7$ T. The $λ$-type anomaly and long-range order persist up to 9 T, showing the reconfiguration of the ground state as opposed to its suppression. Heat-capacity analysis reveals the full $2R\ln2$ magnetic entropy expected for two $J_{\rm eff} = 1/2$ moments per formula unit, confirming the pseudospin description. These findings demonstrate that water intercalation is a robust strategy for tuning the magnetic properties of honeycomb lattice materials. Overall, this study highlights neutral-molecule insertion as a promising route toward the discovery and engineering of quantum magnets based on layered transition metal oxides.
title Crystalline water intercalation into the Kitaev honeycomb cobaltate Na$_2$Co$_2$TeO$_6$
topic Strongly Correlated Electrons
Materials Science
url https://arxiv.org/abs/2508.08717