Investigations of Stacking Faults in Stacked Granular Perpendicular Recording Media With a High-Anisotropy CoPt Layer

Microstructural investigations of granular perpendicular recording media based on stacked CoPt-alloy layers were carried out using high-resolution transmission electron microscopy (HRTEM). In the structure investigated, a thin layer of CoPt with high Pt concentration was inserted to meet the thermal stability requirements at higher densities. The increase in the coercivity and nucleation field of the sample observed for the insertion of a thin layer of CoPt (3 nm), and the decrease beyond this critical thickness has been explained based on HRTEM studies. HRTEM results indicated that the insertion of thicker CoPt layer causes stacking faults and the presence of fcc phase in the CoCrPt layers on the top. The number of stacking faults and the fcc content in grains depend on the thickness of CoPt layer, indicating that the observed changes in magnetic properties arise due to the microstructural changes.