Interlayer exchange coupling in asymmetric Fe(1 1 0)/Cu/Fe(1 1 0) thin films studied by Brillouin light scattering

The magnetic properties of bcc Fe(1 1 0) bilayers separated by fcc(1 1 1) Cu films of variable thickness in the range between 0 and 33 Å have been investigated by Brillouin light scattering. The two Fe films, 20 and 60 Å thick, were grown on the 7×7 reconstructed surface of a Si(1 1 1) substrate using metal–metal epitaxy on silicon. Low-energy electron diffraction analysis revealed that the Fe films consist of bcc(1 1 0) domains in Kurdjumov–Sachs orientation. For Cu interlayer thickness larger than 6 Å, the Brillouin spectrum consists of two spin-wave modes due to the double layered structure which depends on the Cu-layer thickness. The experimental spin-wave frequency dependence on the incidence angle of light has been interpreted using a model that includes both the bulk and the interface first-order anisotropy, as well as the bilinear exchange coupling between the two Fe films. We found that, for the Cu range of thickness investigated, the bilinear coupling is always ferromagnetic, in agreement with the shape of the Kerr hysteresis loops.