EXPONENTIAL BEHAVIOR OF THE INTERLAYER EXCHANGE COUPLING ACROSS NONMAGNETIC METALLIC SUPERLATTICES

It is shown that the coupling between magnetic layers separated by non magnetic metallic superlattices can decay exponentially as a function of the spacer thickness N, as opposed to the usual N-2 decay. This eff ect is due to the lack of constructive contributions to the coupling f rom extended states across the spacer. The exponential behavior is obt ained by properly choosing the distinct metals and the superlattice un it cell composition.