| abstract |
A method of producing high coercivity FePt-Si3N4 granular composite thin films for magnetic recording media is invented. The method includes magnetron co-sputtering of FePt and Si3N4 targets at controlled sputtering power and sputtering argon gas pressure to form a selective composition of granular FePt-Si3N4 thin film on a low temperature substrate, then post-annealed in vacuum at selective time period and temperature. Two kinds of FePt targets can be used. One is the FePt alloy target. The other one is a composite target consisting of an iron disk overlaid with small Pt pieces. This arrangement provides a wide range of effective target compositions and therefore film compositions. FePt-Si3N4 films were deposited on natural oxidized silicon wafer or quartz glass substrate at room temperature. The as-deposited film has soft magnetic properties and granular structure with soft magnetic gamma-FePt particles dispersed in amorphous Si3N4 matrix. The as-deposited film cannot be used as magnetic recording medium due to its low coercivity. After annealing at controlled conditions for a desirable temperature and time period in vacuum, the film also has granular structure but the magnetic soft gamma-FePt phase is transformed into magnetic hard gamma1-FePt phase. This film has high coercivity and its magnetic easy-axis is parallel to the film plane. It may be used as high-density magnetic recording medium. |