  Broadband FMR responses for metallic single-layer and bi-layer magnetic films
with total thicknesses smaller than the microwave magnetic skin depth have been
studied. Two different types of microwave transducers were used to excite and
detect magnetization precession: a narrow coplanar waveguide and a wide
microstrip line. Both transducers show efficient excitation of higher-order
standing spin wave modes. The ratio of amplitudes of the first standing spin
wave to the fundamental resonant mode is independent of frequency for single
films. In contrast, we find a strong variation of the amplitudes with frequency
for bi-layers and the ratio is strongly dependent on the ordering of layers
with respect to a stripline transducer. Most importantly, cavity FMR
measurements on the same samples show considerably weaker amplitudes for the
standing spin waves. All experimental data are consistent with expected effects
due to screening by eddy currents in films with thicknesses below the microwave
magnetic skin depth. Finally, conditions for observing eddy current effects in
different types of experiments are critically examined.
