  There are different mechanisms proposed to be responsible for the temperature
dependence of the interlayer exchange coupling (IEC), namely a smearing out of
the spacer or interface Fermi surface and excitations and interactions of spin
waves. We propose a possibility to separate both effects by calculating the
excitation spectrum of an extended Heisenberg model and connecting the results
with ferromagnetic resonance (FMR) experiments. To solve the Heisenberg model
we use an approximation that was shown to yield excellent results. In this
paper the main idea of this procedure is explained and a detailed investigation
of the spin wave contribution to the temperature dependence of FMR resonance
frequencies and fields is carried out.
