Dependence of perpendicular coercivity on residual stress of Ba ferrite/ZnO bilayered films deposited on fused quartz substrate

Ba ferrite films composed of perfectly c-axis oriented crystallites, perpendicular to film plane, were deposited on fused quartz sheets with ZnO underlayer at substrate temperature of 150°C. It was found that the creation of microcracks due to the large residual stress in the films was sufficiently suppressed by depositing the ZnO layer at a substrate temperature of 450°C and by reducing the thickness of ZnO layer. The stress also increased the perpendicular coercivity due to the magnetostriction effect. These results suggest that the thickness of the Ba ferrite and ZnO layers should be reduced to decrease magnetostrictive demagnetization to be suitable for the application to high density magnetic recording media