Experimentally, the magnetic coupling strength in Co/TM and Fe/TM multilayer systems, for which TM is a nonmagnetic transition metal, increases dramatically as a function of the electron per atom ratio, e/a, in the TM spacer layers. On the basis of simple model calculations we argue that this effect is a finite resonant increase of the coupling due to the variation of the band offset between the TM spacer and the magnetic host. We find that the specific form of the correlation is strongly influenced by the resonant coincidence of the TM bands with either the spin up or the spin down bands of the host, for particular values of e/a. We suggest new experiments to test the model.

• Received 8 January 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.181