The antiferromagnetic and ferromagnetic interlayer coupling across Au(111) has been investigated employing a 2 Å Co/Au/7 Å Co trilayer with the Au spacer layer in the form of a wedge. The sample was deposited by Molecular Beam Epitaxy on a Cu single crystal substrate covered by a Au base layer. A highly localized magneto-optical Kerr effect hysteresis loop study revealed an oscillatory coupling extending to Au thicknesses of 40 Å. The period was found to increase markedly with increasing Au thickness, whereas a more than quadratic decrease of the coupling strength with increasing Au thickness was observed. © 1994.