We present an $S=1/2$ antiferromagnetic (AF) honeycomb lattice composed of a verdazyl-based complex $\left[\mathrm{Zn}{\left(\mathrm{hfac}\right)}_2\right][o$-Py-V-(4-${\mathrm{F})}_2]$. Ab initio molecular orbital calculations indicate that two AF interactions and a ferromagnetic interaction lead to the formation of a honeycomb lattice. We explain the magnetic susceptibility, magnetization curve, and magnetic specific heat based on the $S$ = 1/2 Heisenberg AF honeycomb lattice using the quantum Monte Carlo method. Further, by considering the distortion effect on the magnetic behavior, we confirm that the dimer-like lattice distortion in the present compound is small enough not to affect the intrinsic two-dimensional properties of the honeycomb lattice. Our numerical study on the distorted honeycomb lattice reveals a quantum phase transition from a disordered dimer phase to an AF ordered phase at a critical distortion ratio.

• Received 8 September 2019
• Revised 7 January 2020

DOI:https://doi.org/10.1103/PhysRevB.101.014437