Effects of composition control on crystallographic and magnetic characteristics of Ba ferrite films sputtered with the mixture of Xe, Kr, Ar, and O2 for recording media

Abstract

Ba ferrite/ZnO bilayered films were deposited by plasma-free sputtering method using the mixture of Xe, Kr, Ar, and O2 as sputtering gas. The discrepancy in the film composition and changes in crystallographic and magnetic characteristics corresponding to the partial gas pressure and gas species were investigated in detail. The plasma diagnosis implied that the severe bombardment of recoiled Ar atoms and energetic sputtered particles to the surface of the film and the selective resputtering of Ba atoms were suppressed by adding Xe into sputtering gas. Ba ferrite films with excellent characteristics were deposited using the mixture of Ar, Xe, and O2 as sputtering gas when the sticking coefficient of Ba atoms on the film surface took the maximum value, while the bombardment to the film surface was negligible and the film composition was almost stoichiometric. On the other hand, although the substitution of Kr for Ar is effective for suppressing the bombardment to the surface, the energy of the arriving Ba and Fe atoms reduced and it caused the smaller sticking coefficient of Ba atom and the worse characteristics.