Interlayer exchange coupling in asymmetric Fe(110)/Cu/Fe(110) thin films studied by Brillouin light scattering

The magnetic properties of bcc Fe(1 1 0) bilayers separated by fcc(1 1 1) C u films of variable thickness in the range between 0 and 33 Angstrom have b een investigated by Brillouin light scattering. The two Fe films, 20 and 60 Angstrom thick, were grown on the 7 x 7 reconstructed surface of a Si(1 I 1) substrate using metal-metal epitaxy on silicon. Low-energy electron diff raction analysis revealed that the Fe films consist of bcc(1 1 0) domains i n Kurdjumov-Sachs orientation. For Cu interlayer thickness larger than 6 An gstrom, the Brillouin spectrum consists of two spin-wave modes due to the d ouble layered structure which depends on the Cu-layer thickness. The experi mental spin-wave frequency dependence on the incidence angle of light has b een 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 shap e of the Kerr hysteresis loops. (C) 2001 Elsevier Science B.V. All rights r eserved.