  We constructed a quasi-analytical self-consistent model of the
stripline-based broadband ferromagnetic resonance (FMR) measurements of
ferromagnetic films. Exchange-free description of magnetization dynamics in the
films allowed us to obtain simple analytical expressions. They enable quick and
efficient numerical simulations of the dynamics. With this model we studied the
contribution of radiation losses to the ferromagnetic resonance linewidth, as
measured with the stripline FMR. We found that for films with large
conductivity of metals the radiation losses are significantly smaller than for
magneto-insulating films. Excitation of microwave eddy currents in these
materials contributes to the total microwave impedance of the system. This
leads to impedance mismatch with the film environment resulting in decoupling
of the film from the environment and, ultimately, to smaller radiation losses.
We also show that the radiation losses drop with an increase in the stripline
width and when the sample is lifted up from the stripline surface. Hence, in
order to eliminate this measurement artifact one needs to use wide striplines
and introduce a spacer between the film and the sample surface. The radiation
losses contribution is larger for thicker films.
