Dipolar anisotropy in quadratic-layer antiferromagnets

Dipolar interactions in quadratic-layer Heisenberg antiferromagnets have been treated in the spin-wave approximation to calculate the temperature dependence of the sublattice magnetization and the magnon energy gap. Magnon-magnon interactions are included to first order. Numerical results for K₂{MnF}₄$ and the double-layer ${K}₃Mn₂{F}₇$ confirm the earlier spin-wave analyses of these structures, in which the $k=0$ magnon energies were made dependent on temperature in a semi-empirical way. The gaps as a function of the temperature scale with the sublattice magnetizations.