Interlayer exchange coupling in Fe/Cr multilayers

We investigate the origin of the long-period oscillation of the interlayer exchange coupling in Fe/Cr trilayer systems. Within the stationary phase approximation the periods of the oscillations are associated with extremal vectors of the Fermi sphere of Cr. Using a realistic tight-binding model with spin-orbit interaction we calculate the coupling strength for each extremal vector based on the spin asymmetry of the reflection amplitude for a propagating state impinging from the Cr to Fe layer. We find that for the (001) and (110) growth directions the biggest coupling strength comes from the extremal vector centered at the ellipsoid N of the Fermi surface of Cr.