The cobalt-based honeycomb magnet ${\mathrm{BaCo}}_2{\left({\mathrm{AsO}}_4\right)}_2$ (BCAO) has recently emerged as a promising platform for frustrated magnetism beyond conventional paradigms. Neutron-scattering experiments and first-principles calculations have revealed an unexpected double-zigzag (dZZ) magnetically ordered ground state, whose microscopic origin remains under active debate. Here, we revisit this problem within a ferroantiferromagnetic $J_1–J_3$ Heisenberg model on the honeycomb lattice using a generalized Schwinger-boson mean-field theory that treats ferromagnetic and antiferromagnetic interactions on equal footing. This approach, combined with exact diagonalization, allows us to demonstrate the emergence of the dZZ phase in a narrow parameter range, stabilized by quantum fluctuations through an order-by-disorder mechanism, in good agreement with recent density-matrix renormalization-group results. We further characterize the associated magnetic excitations and discuss their relevance to recent inelastic neutron-scattering measurements on BCAO.

Close

PrevNext

View figure in article

• Frustrated magnetism
• Quantum spin liquid
• Ferromagnets
• Honeycomb lattice
• Heisenberg model
• Schwinger boson method