Exact solutions for inelastic neutron scattering from planar Ising ferromagnets

We report the inelastic neutron scattering from planar Ising ferromagnets. The lattice structures investigated are square, kagomé, triangular, and 3–12 (extended kagomé). Exact solutions are obtained for the inelastic neutron scattering function Sxx(q, ω) of these isotropic Ising ferromagnets at all temperatures. The scattering amplitudes An (n is an integer) of the Dirac δ-functions are plotted as functions of the interaction parameter K (≡ J/kBT). The amplitude curves show “spin wave peaks” at very low temperatures. The amplitude curves for all lattice structures show some general features such as weak energy-type singularities at criticality rounded maxima, crossing points, and a systematic variation versus temperature.