High Coercivity Sr-ferrite Magnetic Thin Films Induced by Various Underlayers

Three kinds of oxide underlayers, namely SiO2, ZnO and Al2O3, were deposited prior to the sputtering of Sr-ferrite films, respectively, in order to induce the optimum grain morphology and the texture of the films. A Sr-ferrite film with an easy axis in-plane orientation was induced by SiO2 underlayer. In contrast, it prefers to be perpendicular to film plane for the cases of ZnO and Al2O3 underlayers. The optimum magnetic properties of the former film along film plane are: 4 pi M-r=1.7 kG, H-i(c)=5.35 kOe, and S-q=0.59, which are mainly dominated by the exchange coupling effect. determined by Wohlfarth's remanence analysis. among grains. White those for the films with an easy axis perpendicular to film plane can be as high as 4 pi M-r=3.72 kG, H-i(c)=6.42 kOe, and S-q=0.82, which are mainly dominated by the magnetostatic interaction among grains.