We have used the polar Kerr effect to investigate the magnetic coupling between two 3-monolayer (ML)-thick ferromagnetic fcc-Fe films separated by a Cu spacer layer in epitaxial Cu60Fe3CuxFe 3Cu(100) structures specially prepared to have atomically sharp interfaces. We have observed concurrent oscillations in the interlayer exchange coupling strength and the zero-ellipticity polar Kerr rotation as a function of x. The oscillation in exchange coupling covers at least four periods (x=0-30 ML), and has a phase consistent with antiferromagnetic coupling in the limit of zero-Cu-spacer-layer thickness. Preliminary evidence indicates that the oscillation in exchange coupling is not only in magnitude, but may involve alternation between antiferromagnetic and ferromagnetic states. We note the similarity between two distinct magnetic/nonmagnetic layered systems: Co/Ru 1 and our Fe/Cu/Fe, both of which exhibit oscillations in the magnitude of the exchange coupling with periods of ∼7 ML, and have phases consistent with antiferromagnetic coupling in the limit of zero-spacer-layer thickness. Finally, our samples exhibit a major enhancement in the Kerr rotation over that expected on the basis of plasma resonant absorption. Close correlation of this enhancement with the strength of the interlayer magnetic coupling suggests a common mechanism for these effects.
