Abstract: A servo pattern has bursts that are constructed from two frequencies in a complementary arrangement so that the servo pattern frequencies alternate in adjacent servo tracks. The servo pattern is decoded by a pair of digital notched filters so that each filter notches out readback signal data from a different one of the frequencies to form a combined PES signal produced from each respective frequency and to control movement of the head servo. The complementary arrangement of the servo bursts decreases signal gain differences between the frequencies and improves the accuracy of servo position information. The digital notched filter provides efficient processing of the readback signal and enhances easier selection of filter parameters and easier design of the servo processing circuitry. The servo pattern uses less disk surface area as compared with typical dual or quadrature servo patterns and can be recorded on the disk using fewer servo write steps.

Abstract: A significantly thinner boron carbide overcoat layer is provided for a magnetic disk which has the same durability as thicker prior art overcoat layers for protecting an underlying magnetic layer. By employing adhesion layers selected from the group consisting of Ge, Ru, WTiSi, WTi, Si, and Y between the magnetic layer and the overcoat layer, the durability of the overcoat layer is significantly increased over a single overcoat layer of B4C. Certain process steps in the making of the B4C overcoat layer still further enhance the durability of the B4C overcoat layer by maintaining the disk or substrate specimen at a floating potential in a plasma chamber and employing low levels of argon pressure and sputtering wattage.