Three-layer FeNi/Dy/FeNi films were studied by the ferromagnetic resonance method in the temperature range from 4 to 300 К. The detected acoustic and optical peaks in the microwave absorption spectra demonstrate that there is exchange coupling between the ferromagnetic FeNi layers of the planar system, which allows us to define the sign and value of the interlayer exchange interaction constant. The temperature dependences of the interlayer exchange constant of the three-layer films with an interlayer thickness of Dy equal to 5 and 10 nm show a number of features (change of the sign and extreme point) which reflect the transformation of the Dy magnetic structure

The spectrums of standing exchange spin waves into magnetic sandwich Ni80Fe20/Cu(tCu)/Ni80Fe20 were studied by spin-wave resonance method. The layer of diamagnetic Cu depending on its thickness tCu provided both positive and negative exchange interaction between ferromagnetic layers. It was shown that spin waves modes of SWR spectra which are described by well-known relation Hres(n)~n^2 are standing acoustic exchange spin oscillations of individual ferromagnetic layers, regardless of a sign of interlayer exchange couple. It was detected that spin modes which are optical satellites of acoustic SWR peaks are described by the dependence of the resonance field Hres(n)~n^(5/2) or Hres(n)~n^2 depending on the boundary conditions established on inner interfaces.