Magnetic excitations of undoped iron oxypnictides

We study the magnetic excitations of undoped iron oxypnictides using a three-dimensional Heisenberg model with single-ion anisotropy. Analytic forms of the spin-wave dispersion, velocities, and structure factor are given. Aside from quantitative comparisons that can be made to inelastic neutron scattering experiments, we also give qualitative criteria that can distinguish various regimens of coupling strength. The magnetization reduction due to quantum zero point fluctuations shows clear dependence on the c-axis coupling.