With varying thickness of the spacer near the second oscillatory GMR peak in Co/Cu system, a series of glass/Fe/[Co/Cu]20/Co multilayers are prepared by magnetronsputtering technique. The MR values are relatively small. High angle X-ray di raction shows that the copper crystallizes in fcc structure with (111) texture and the cobalt crystallizes in hcp structure with (002) preferential orientation. There is a mixed amorphous CoCu layer at the interface due to the di usion between cobalt and copper, which may decrease the MR value. The thickness, the mass density for each sub-layer and the surfacial and interfacial roughnesses are re ned from the X-ray specular reflectivity measurement.