ハニカム格子構造が量子材料開発を加速（Honeycomb lattice sweetens quantum materials development）

2026-01-16 オークリッジ国立研究所（ORNL）

In a honeycomb lattice of potassium cobalt arsenate, cobalt spins (red and blue arrows) couple and align. Potassium, arsenic and oxygen are removed to highlight the magnetic cobalt atoms. Credit: Adam Malin/ORNL, U.S. Dept. of Energy

＜関連情報＞

• https://www.ornl.gov/news/honeycomb-lattice-sweetens-quantum-materials-development
• https://pubs.acs.org/doi/full/10.1021/acs.inorgchem.5c00932

準安定コバルトハニカムKCoAsO4の合成と特性評価 Synthesis and Characterization of Metastable Cobalt Honeycomb KCoAsO4

Lucas A. Pressley,Colin L. Sarkis,Justin Felder,Clarina R. Dela Cruz,Raymond R. Unocic,Zheng Gai,Jeffrey D. Einkauf,Saurabh P. Pethe,Mariappan P. Paranthaman,Tom Berlijn,John W. Villanova,Satoshi Okamoto,Michael A. McGuire,D. Alan Tennant,Stephen E. Nagler,and Craig A. Bridges
Inorganic Chemistry  Published: June 27, 2025
DOI:https://doi.org/10.1021/acs.inorgchem.5c00932

Abstract

The Kitaev model has served as a long-sought-after target in the realization of a quantum spin liquid that could host Majorana Fermions. Such non-Abelian anyons could revolutionize quantum computing if properly implemented to overcome decoherence. A 3d⁷ electronic configuration, like Co²⁺, has been explored by theory and experimental work to design Kitaev materials. Here, we report the synthesis of a new cobaltate honeycomb material KCoAsO₄. The compound is synthesized through a low-temperature solution route and crystallized in space group R¯3 with lattice parameters a = 5.0394(1) and c = 28.6790(1) as determined by neutron powder diffraction. The crystal structure follows motifs similar to those of the honeycomb compound BaCo₂(AsO₄)₂ but presents differing magnetic behavior. Magnetization/heat capacity measurements on the powder show antiferromagnetic transition T_N = 14 K. Two lower-temperature transitions are present in susceptibility at low field that resemble spin reorientations. Magnetization data as a function of field have curvature indicative of metamagnetic behavior below the magnetic ordering temperature, with the magnetic ordering suppressed upon application of a higher magnetic field. Computational studies suggest the presence of a weak nearest-neighbor Kitaev term, K₁, consistent with related honeycomb cobaltates. Together, the data suggest that this material should present a new platform for developing Kitaev quantum spin liquids.