Despite the large lattice mismatch (≃8%), we demonstrate the growth of epitaxially ordered Co/Ru superlattices consisting of hcp (0001) Co and Ru sublayers. For small Ru interlayer thickness, a large antiferromagnetic exchange coupling between the Co sublayers is observed that influences strongly the magnetization process, as the magnetization within Co sublayers can no longer be considered to be fully locked ferromagnetically. For small Co and Ru thicknesses, the magnetization is oriented along the film normal, while the adjacent Co layers are strongly coupled antiferromagnetically. For this peculiar magnetic structure, a first-order spin-flop transition from an antiferromagnetic state to a ferromagnetic canted state is observed and clearly revealed by use of a ferromagnetic-resonance technique.

• Received 26 September 1991

DOI:https://doi.org/10.1103/PhysRevB.45.7768