Magnetic properties of amorphous Co0.74Si0.26∕Si multilayers with different numbers of periods

Two sets of [Co0.74Si0.26(5nm)∕Si(s)]n amorphous films were prepared by magnetron sputtering: one in the form of multilayers with the Si spacer thickness s fixed at 3nm, and the number n of periods varying from 1 to 10 and the other with only two periods and s varying from 3to24nm (trilayers). In both sets, the Co0.74Si0.26 layer thickness t was fixed at 5nm. All the samples except the one with s=24nm manifest antiferromagnetic coupling. Their magnetic properties at room temperature were probed using the magnetooptical transverse Kerr effect (MOTKE) and ferromagnetic resonance (FMR). The relative increase in the saturation magnetization Ms (for trilayers, relative to a structure with s=24nm; for multilayers, relative to the single-layer structure) determined from the FMR measurements was compared with the exchange coupling strength HJAF obtained from the MOTKE studies. The dependences of HJAF and Ms on n and s were found to be very similar to each other. Possible mechanisms of this similarity are discussed.