Interlayer exchange interactions in Co/Ru/CO trilayer structures were
investigated by ferromagnetic resonance and in-plane magnetization mea
surements. Oscillations in the exchange coupling between the two Co la
yers were observed with the variation of the Ru thickness. The FMR spe
ctra in the strongly anti-parallel coupled films were significantly mo
dified from that of a single layer system and the observations are in
excellent agreement with previous predictions.