Brillouin light scattering study of ferromagnetically coupled Cu/Fe(110)/Cu/Fe(110)/Cu/Si(111) heterostructures: Bilinear exchange magnetic coupling

Epitaxial Cu(60 Angstrom)/Fe(20 Angstrom)/Cu(d(Cu))/Fe(60 Angstrom)/Cu(60 A ngstrom) heterostructures with the Cu spacer thickness d(Cu) ranging betwee n 0 and 33 Angstrom have been frown on 7 x 7 reconstructed surface of Si(11 1) substrates. Fcc(lll) Fe films grow epitaxially on the Cu(lll) buffer lay er up to a thickness of 6-8 A, while, for larger thicknesses, one observes the appearance of three-dimensional bcc Fe(110) domains in the Kurdjumov-Sa chs orientation. Brillouin light scattering (BLS) from thermally excited sp in waves has been exploited in order to study the interlayer exchange coupl ing between the two Fe films at room temperature. The experimental spin-wav e frequency dependence on the applied magnetic field is simulated using a s imple model which includes first-order intrinsic volume and interface aniso tropies and takes the bilinear exchange interaction between the two ferroma gnetic layers into account. We have found that for thicknesses of the Cu sp acer larger than 6 Angstrom, the Brillouin spectrum consists of two spin-wa ve modes due to the Fe double layered structure which depends on the Cu-lay er thickness. The coupling is found to be ferromagnetic for the whole range of Cu spacer thicknesses investigated. Using the magnetic parameters deter mined by the above analysis, we have carried out a detailed calculation of the BLS cross section assuming the dynamic magnetization to be constant acr oss each magnetic film. A very good agreement between the calculated and th e measured cross sections has been obtained.