Simple theory of exchange coupling in transition-metal magnetic multilayers

Abstract
Several experiments on a variety of magnetic multilayer and sandwich structures have revealed an indirect exchange coupling between layers of ferromagnets separated by nonmagnetic spacer layers. This coupling oscillates from ferromagnetic to antiferromagnetic depending on the thickness of the spacer layers, with an anomalously long period. We study a simple model to explain the long period and compare our results with the Ruderman-Kittel-Kasuya-Yosida theory of indirect exchange coupling.