Magnetic Excitations of Spin-Gap System Na3Cu2SbO6 with Distorted Honeycomb Structure

Magnetic excitation spectra of quantum spins of Na3Cu2SbO6 with a distorted honeycomb structure have been measured by neutron inelastic scattering. The intensity distribution and the dispersion curves of the excitations indicate that the spin system can be well understood by considering one-dimensional spin chains, formed of Cu2+ ions on a lattice of alternating the shorter and longer spacings along the b-axis. The exchange interactions between the neighboring spins with the shorter and longer spacings correspond to ferromagnetic and anti ferromagnetic interactions, respectively. These findings are consistent with those we reported previously on the basis of macroscopic measurements. The observed gap Delta(G) is 8.9 meV and the energies of the antiferromagnetic and ferromagnetic interactions have been found to be 13.9 and - 12.5 meV. respectively.