The results of a complex microstructural analysis of periodic metallic magnetic multilayer systems (MLS) by Scanning/Transmission Electron Microscopy, Energy Dispersive X-ray microanalysis and Resonant X-ray Reflectivity (RXRR) are presented. The crystal structure of MLS based on Cr-Gd-Cr-Fe layers with different Cr layer thicknesses was revealed. The use of RXRR at the Cr and Fe absorption edges significantly improves the optical contrast between correspondent layers. A significant Cr diffusion was detected in adjacent layers. After that diffusion, Fe and Gd layers transformto the solid solution of Cr in Fe and in Gd respectively, without changing their crystal structure. Such Cr behaviormay affect both the exchange coupling between Fe and Gdmagneticmoments and the structural parameters of Gd layers, thus influencing drastically the magnetic moment. (C) 2017 Published by Elsevier B.V.