Exponential behavior of the interlayer exchange coupling across nonmagnetic metallic superlattices

It is shown that the coupling between magnetic layers separated by nonmagnetic metallic superlattices can decay exponentially as a function of the spacer thickness $N,$ as opposed to the usual $N^{-2}$ decay. This effect is due to the lack of constructive contributions to the coupling from extended states across the spacer. The exponential behavior is obtained by properly choosing the distinct metals and the superlattice unit cell composition.