Characterization of the magnetic modification of Co/Pt multilayer films by He+, Ar+, and Ga+ ion irradiation

Co/Pt multilayers can exhibit large perpendicular anisotropies and coercivities that are very sensitive to the quality of the Co/Pt interfaces. We have characterized the dependence of coercivity of Co/Pt multilayers on irradiation with various ion species (He+, Ar+, and Ga+), energies (20 keV–2 MeV), and doses (1011–1017 ions/cm2), in order to understand better the nature of the structural changes responsible for the magnetic changes. We find that, in general, the system is much more sensitive to irradiation than expected on the basis of a nearest-neighbor coupling model and simple ballistic ion-beam mixing.