A study of interlayer coupling in Co/Cu multilayers

Co(22 Å)/Cu multilayers with Cu thicknesses varying from 6 to 40 Å are studied by vibrating-sample magnetometry and ferromagnetic-resonance spectroscopy (FMR). The magnetization was found to increase with decreasing Cu thickness, whereas the linewidth of the uniform mode of the FMR was found to decrease. This is attributed to the spin polarization of the Cu layers due to interlayer coupling and its effect on the lowered dimensionality of the Co layers. We also observed a peak on the high-field side of the uniform FMR mode, which we attribute to antiparallel coupling of adjacent ferromagnetic layers producing an ‘‘optical’’ mode.