Oscillations of Interlayer Exchange Coupling vs. Ferromagnetic-Layers Thickness

The dependence on the ferromagnetic-layers thickness of interlayer exchange coupling between ferromagnetic layers separated by a paramagnetic spacer is discussed. It is shown that an oscillatory behaviour should show up, due to Fabry-Pérot-like interferences of the electron Bloch waves in the ferromagnetic layers. This behaviour appears clearly from the analytical expression of the exchange coupling, as well as from numerical calculations for a simple, physically transparent, free-electron model. Finally, the case of Co/Cu/Co(001) is discussed.