The magnetic properties of ferromagnetic bilayers Co90Fe10/Ni81Fe19, Ni81Fe19/Co90Fe(10), and monolayer Ni81Fe19 thin films with individual layer thicknesses of 2 nm and 5 nm were grown on thermally oxidized Si substrate have been investigated by a ferromagnetic resonance (FMR) technique at room temperature. The FMR spectra were recorded for both parallel geometry, where the applied DC magnetic field in the surface of the films and perpendicular geometry with the magnetic field perpendicular to surface. The FMR resonance field were analyzed and fitted theoretically by using the dispersion relation with the Bloch - Bloembergen damping term. Computer programs have been written to extract the theoretical magnetization (M), resonance field values (H-r) and spin-spin relaxation time (T) fit parameters. Experimental and theoretical analyses showed that the order of bilayers with respect to the substrate creates remarkable effects on the magnetization properties due to changing continuity of structure on the substrate. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.