Oscillatory exchange coupling with a period of two Fe monolayers in Au/Fe/Au/Fe/Au(001)

The dependence of the interlayer exchange coupling across a Au spacer on Fe-layer thickness has been investigated for molecular-beam-epitaxy grown Au/Fe/Au/Fe/Au(001) films involving two step-shaped Fe layers with each step 1 ML high. The coupling strength oscillates as a function of each Fe-layer thickness with a period of 2 ML Fe, maintaining the Au-layer thickness dependence. The oscillation is attributed to the resonance state involving the Fe majority-spin ${\mathrm{\Delta }}_1$ band. The fact that the oscillation with a period of ∼6 ML Fe, which appeared in the Fe/Cr(001) system, is not observed in this Fe/Au(001) system is important; it indicates that the connection between the interference wave vector inside the Fe layers and in the spacer responsible for the coupling is important for quantum interference in the ferromagnetic layers.