Using a recently developed method for calculating series expansions of the excitation spectra of quantum lattice models, we obtain the spin-wave spectra for square lattice, S=1/2 Heisenberg-Ising antiferromagnets. The calculated spin-wave spectrum for the Heisenberg model is close to but noticeably different from a uniformly renormalized classical (large-S) spectrum with the renormalization for the spin-wave velocity of approximately 1.18. The relative weights of the single-magnon and multiple-magnon contributions to neutron-scattering spectra are obtained for wave vectors throughout the Brillouin zone.

• Received 8 September 1995

DOI:https://doi.org/10.1103/PhysRevB.52.R15695