Oscillatory interlayer exchange coupling of Co/Ru and permalloy / Ru multilayers investigated by Brillouin light scattering

We have determined the absolute value of the interlayer exchange coupling constant A12 of sputtered Co/Ru and permalloy/Ru multilayers using Brillouin light scattering. The spin wave frequencies and therefore A12 are found to oscillate as a function of the Ru layer thickness in both multilayer systems with a period of 11.5 å. The amplitudes of the oscillations in A12 are found to be smaller by a factor of 2 in permalloy/Ru compared to Co/Ru, which scales with the smaller saturation magnetization in permalloy. Contrary to the Co/Ru system we found evidence for a short period oscillation in permalloy/Ru. Detailed calculations show that the spin-wave frequency oscillations result from the canting of layer magnetizations in the antiferromagnetic coupling regimes. © 1993.