We report crystal structure and magnetic behavior of the triangular antiferromagnet ${\mathrm{KYbO}}_2$, the A-site substituted version of the quantum spin liquid candidate ${\mathrm{NaYbO}}_2$. The replacement of Na by K introduces an anisotropic tensile strain with 1.6% in-plane and 12.1% out-of-plane lattice expansion. Compared to ${\mathrm{NaYbO}}_2$, both Curie-Weiss temperature and saturation field are reduced by about 20% as the result of the increased Yb-O-Yb angles, whereas the $g$ tensor of ${\mathrm{Yb}}^{3+}$ becomes isotropic with $g=3.08\left(3\right)$. Field-dependent magnetization shows the plateau at $\frac{1}{2}$ of the saturated value and suggests the formation of the up-up-up-down field-induced order in ${\mathrm{KYbO}}_2$ in contrast to the more common $\frac{1}{3}$ plateau with the up-up-down order that has been reported in the isostructural ${\mathrm{Yb}}^{3+}$ selenides.

• Received 23 March 2023
• Revised 12 May 2023
• Accepted 17 May 2023

DOI:https://doi.org/10.1103/PhysRevB.107.224416