Preparation of double layer hexagonal ferrite films for high density longitudinal magnetic recording media

The deposition of the hexagonal ferrite films hopeful for high density recording has been attempted by means of Targets-Facing Type(TFT) of sputtering apparatus. The sputtering conditions and the concentration of sputtered films were investigated. The difference in composition between targets and deposited film becomes larger when the substrate temperature is elevated above 600°C. In order to obtain the films with stoichiometric composition, it is necessary to adjust the composition of target. If the films of hexagonal ferrite such as Co2Z type are desired, the substrate temperature Ts should be very high because the activation energy of the constitutes of Co2Z system is high. An undesirable reaction takes place easily between sputtered particles and SiO2surface layer of SiO2/Si substrate. In that case, cobalt silicate and barium silicate were formed in the films deposited at Ts above 700°C. As a under layer for preventing such a reaction, Al2O3, ZnO, and AlN films has been examined. The films deposited at Ts of 700°C, included BaM phase with good orientation of c-axis normal to the film plane but most desirable Co2Z phase. Magnetic property of the film deposited on SiO2/ Si substrate were 1∼3kOe in coercivity (in plane) Hc ,0.6∼0.9 in squareness S, and 160∼260 emu/cm³in saturation magnetization Ms.