Competing Antiferromagnetic-Ferromagnetic States in d7 Kitaev Honeycomb Magnet

Published

December 14, 2020

Author(s)

Hector Vivanco, Benjamin Trump, Craig Brown, Tyrel M. McQueen

Abstract

The Kitaev model is a rare example of an analytically solvable and physically instantiable Hamiltonian yielding a topological quantum spin liquid ground state. Here we report signatures of Kitaev spin liquid physics in the honeycomb magnet Li₃Co₂SbO₆, built of high-spin d⁷ (Co²⁺) ions, in contrast to the more typical low-spin d⁵ electron configurations in the presence of large spin-orbit coupling. Neutron powder diffraction measurements, heat capacity, and magnetization studies support the development of a long-range antiferromagnetic order space group of C_C2/m, below T_N = 11 K at υ₀H = 0 T. The magnetic entropy recovered between T = 2 K and 50 K is estimated to be 0.6Rln2, in good agreement with the value expected for systems close to a Kitaev quantum spin liquid state. The temperature-dependent magnetic order parameter demonstrates a β value of 0.19(3), consistent with XY anisotropy and in-plane ordering, with Ising-like interactions between layers. Further, we observe a spin-flop driven crossover to ferromagnetic order with space group of C2/m under an applied magnetic field of υ₀H ≈ 0.7 T at T = 2 K. Magnetic structure analysis demonstrates these magnetic states are competing at finite applied magnetic fields even below the spin-flop transition. Both the d⁷ compass model, a quantitative comparison of the specific heat of Li₃Co₂SbO₆, and related honeycomb cobaltates to the anisotropic Kitaev model further support proximity to a Kitaev spin liquid state. This material demonstrates the rich playground of high-spin d⁷ systems for spin liquid candidates, and complements known d⁵ Ir- and Ru-based materials.

Citation

Physical Review B

Volume

102

Issue

22

Pub Type

Journals

Keywords

Magnetism, Kitaev Modeling, Honeycomb Magnets, Frustrated Magnetism

Citation

Vivanco, H. , Trump, B. , Brown, C. and McQueen, T. (2020), Competing Antiferromagnetic-Ferromagnetic States in d⁷ Kitaev Honeycomb Magnet, Physical Review B (Accessed October 14, 2025)