Top surface roughness and interface roughness are one of the key elements which determine the perfor-mance of X-ray and neutron thin film multilayer devices. It has been observed that by mixing air withargon in sputtering ambience during deposition of Co layers, polarized neutron reflectivity (PNR) of Co/Tisupermirror polarizers can be improved substantially. Cross-sectional HRTEM measurement reveals thatsharper interfaces in the supermirror can be achieved in case of deposition of the multilayer under mixedambience of argon and air. In order to investigate this interface modification mechanism further, in thiscommunication two sets of tri-layer Co/Ti/Co samples and 20-layer Co/Ti periodic multilayer sampleshave been prepared; in one set all the layers are deposited only under argon ambience and in the otherset, Co layers are deposited under a mixed ambience of argon and air. These samples have been character-ized by measuring specular and non-specular X-ray reflectivities (GIXR) with X-rays of 1.54˚A wavelengthand polarized neutron reflectivity (PNR) with neutron of 2.5˚A wavelength at grazing angle of incidence.It has been observed that the X-ray and neutron specular reflectivities at Bragg peaks of 20 layer periodicmultilayer increase when Co layers are deposited under mixed ambience of argon and air. The detailinformation regarding the effect of air on the interfaces and magnetic properties has been obtained byfitting the measured spectra. The above information has subsequently been supplemented by XRD andmagnetic measurements on the samples. XPS and XANES measurements have also been carried out toinvestigate whether cobalt oxide or cobalt nitride layers are being formed due to use of air in sputteringambience.