A series of trilayers of sputtered Fe/Si/Fe were grown to study the interface characteristics and magnetic coupling between ferromagnetic Fe layers (30 ? thick) for Si spacer thickness (tSi) ranging from 15 ? to 40 ?. Grazing incidence x-ray diffraction, AFM, resistivity and x-ray photoelectron spectroscopy (XPS) meas-urements show substantial intermixing between the layers during deposition which results in trilayers of complicated structures for different sub-layer thicknesses. A systematic variation in silicide concentration across the interface is observed by XPS measurements. The Fe layers in the trilayers were observed to con-sist of Fe layers doped with Si, ferromagnetic Fe-Si silicide layers and nonmagnetic Fe-Si silicide interface layer, while the Si spacer was found to be Fe-Si compound layers with an additional amorphous Si (α-Si) sublayer for tSi≥ 30 ?. A strong anti-ferromagnetic (AF) coupling was observed in trilayers with iron silicide spacers, which disappeared if α-Si layers present in the spacers. The observed magnetization behaviour in each case is interpreted in terms of changes in interfacial structural and electronic properties due to variation in film thickness.