Role of bound states of magnetic layers in the theory of multilayer interaction

Using planar Dirac delta functions to describe the coupling of magnetic layers to an electron gas, the interaction between the layers is calculated. Both the bound and free states give contributions which are shaped by the range of the bound states. Due to a remarkable cancellation of terms the combined result does not show this shape. In fact, it differs appreciably from the weak-coupling limit only when the binding energy of the bound states is comparable or larger than the Fermi energy.