Abstract : The present paper reports the structural and magnetic properties of sputter deposited (SiO2/Co/Pt/SiO2) n multilayers deposited by magnetron sputtering on quartz substrates as a function of the number of layers (n=1, 2, 3, 4) and the effect of swift heavy ions (120 MeV Ag+9) irradiation on them. The deposition of multilayers was performed under high vacuum on substrates held at 7800 C. All the deposited films were found to contain stoichiometric (Co50 Pt50) particles with L10 ordered structure and their coercivity increases with the increasing number of layers. The formation of L10 ordered structure was evidenced by the presence of (001), (110) super lattice peaks in XRD patterns and from selected area electron diffraction pattern images in TEM. The coercivity of these films was measured using SQUID magnetometer. Irradiation of these films induced an increase in coercivity together with a loss of chemical ordering in the metal phase. However, the easy axis of magnetization remained in the film plane contrary to the case of FePt particles in silica matrix as previously reported.