Resumen
We consider the interlayer exchange coupling between two ferromagnetic layers mediated by a nonmagnetic spacer layer. We adopt the theoretical model which is based on a macroscopic description using the Landau--Lifshitz equations and the Hoffmann boundary conditions characterizing the interlayer exchange coupling between the interfaces of the ferromagnetic films. An asymptotic study of such a layered system for either small or large spacer thicknesses is presented. The asymptotic problem and the boundary conditions at interfaces both for the magnetization and the magnetic field are characterized. Key words. thin films, magnetic multilayers, bilinear coupling, Hoffmann's boundary condition, thin and thick nonmagnetic spacers