  We investigate the effect of eddy currents on ferromagnetic resonance (FMR)
in ferromagnet-normal metal (FM/NM) bilayer structures. Eddy-current effects
are usually neglected for NM layer thicknesses below the microwave (MW) skin
depth (approx. 800 nm for Au at 10 GHz). However, we show that in much thinner
NM layers (10-100 nm of Au or Cu) they induce a phase shift in the FMR
excitation when the MW driving field has a component perpendicular to the
sample plane. This results in a strong asymmetry of the measured absorption
lines. In contrast to typical eddy-current effects, the asymmetry is larger for
thinner NM layers and is tunable through changing the sample geometry and the
NM layer thickness.
