[en] In the present work, (Fe/Cr/Al)x10 multilayer having different thicknesses were deposited using electron beam evaporation in an UHV chamber and were irradiated with 120 MeV Ag⁹⁺ ions to observe change in structural and magnetic properties at interface. X-ray reflectivity measurement shows that the height of Bragg peak deceases fast for lower thickness than the higher thickness. The diffusion length L2 d as a function of ion fluence indicates that the mixing is higher for lower multilayer thickness as compare to higher. Magneto-optic Kerr effect (MOKE) shows Fe/ Cr/Al multilayers are soft in nature and have different in-plane anisotropy in as-deposited multilayers. As a function of fluence, coercivity trend has been observed opposite for different thickness of Fe/Cr/Al multilayer due to different interface mixing. Fe and Cr K-edges x-ray absorption fine structure (XAFS) were used to determine local Fe-Fe and Fe-Cr coordination number, distortion in bond distance and Debye-Waller (DW) factor as a function of multilayer thickness and mixing due to ion beam irradiation. The multilayer thickness dependence mixing can be understood in terms of the thermal spike model by taking into consideration the changes in the electron mobility due to scattering from surface and interfaces