Neutron Scattering Study of a Co2+ Quantum Spin Liquid Candidate Material

Recently, a new generation of honeycomb materials based on the low spin 3d7 Co2+ has been proposed to host quantum spin liquids. We present an inelastic neutron scattering study of a low spin Co material that has originally attracted interest due to its potential to host quantum spin liquids. We identified a bipartite up-down magnetically ordered ground state on the honeycomb backbone of the system, that shows no sharp transitions in susceptibility or specific heat measurements. Observed spin excitations are broad in the reciprocal space in the 0 T field due to the geometric frustration, but spin waves develop under applied magnetic fields. We modeled the system using linear spin-wave theory and determined the exchange parameters.