X-ray studies on the structure and magnetism of the honeycomb cobaltate Na₃Co₂SbO₆ under pressure.

The layered, honeycomb Na₃Co₂SbO₆ material features Co²⁺ ions in trigonally distorted (Δ ∼ 40 meV) edge-shared octahedra [1,2]. The pseudospin-1/2 state of Co²⁺ ions together with edge-shared octahedra introduces Kitaev interactions, and it is predicted [3] that tuning Δ under isotropic compression or uniaxial strain would drive a transition from antiferromagnetically ordered to a spin liquid phase. We conducted X-ray diffraction and X-ray magnetic circular dichroism (XMCD) experiments as a function of hydrostatic pressure in a diamond anvil cell to explore the evolution of Na₃Co₂SbO₆ structure and magnetism. Preliminary results from powder diffraction show no phase transitions up to 70 GPa. Co K-edge XMCD measurements show a robust magnetic ordering up to at least 36 GPa, with an increase in the magnetic ordering temperature with pressure. Higher hydrostatic pressures, or application of uniaxial strain in single crystalline samples, would be needed to sufficiently suppress the trigonal distortion in order to reach the postulated spin liquid phase.

[1] Viciu et al, J. Solid State Chem. 180, 1060 (2007).

[2] Yan et al, Phys. Rev. Mat. 3, 074405 (2019).

[3] Liu et al, Phys. Rev. Let. 125, 047201 (2020).