Al substituted Ba ferrite films with high coercivity and excellent squareness for low noise perpendicular recording layer

Al substituted BaM (Al-BaM) ferrite films with composition of BaAlxFe12-xO(19) (x = 0,1,2) were deposited using facing targets sputtering apparatus on SiOx/Si wafers with a Pt seed layer. A postannealing process is necessary to crystallize the films. It was confirmed that the substrate temperature T-s is also one of the important parameters for the magnetic properties of the postannealed films. Al-BaM ferrite films exhibit the T-s dependence of magnetic properties different from that of simple BaM ones. With increase of the Al content x in Al- BaM ferrite films, 4 pi M-s decreased, while H-c and the anisotropy field H-A increased. It was found that acicular shape grains formed more easily in Al- BaM ferrite films than in simple BaM ones. The squareness S' increased largely by substitution of Al for Fe. The Al- BaM ferrite films with high H-c perpendicular to (similar to 3 kOe) and large S-perpendicular to (similar to 0.9) may be applicable as perpendicular magnetic recording layers with low noise level. (C) 1999 American Institute of Physics. [S0021-8979(99)68508-5].