For conventional Co-alloy perpendicular media, improved designs to maximize writability and thermal stability are critical to the next generation product. Both ECC and CGC media designs are known to improve these factors compared to prior SL media. Optimization of an ECC+CGC media design is complicated by the materials limitation on the maximum available Hk of Co-alloys. With this limitation, a significant percentage of the recording layer must be as hard as possible, and the “soft” layers are required to have sufficient anisotropy to add some KuV stability to the overall structure, as well as maintain a relatively high average Hk to match the head field. At the same time, these layers must still provide the maximum available writability enhancement. These factors drive the importance of the described ECC+CGC media optimizations in designing extendable perpendicular recording media. The key factors outlined point to a different optimal media design
regime than has been previously described for materials with unlimited hard layer anisotropy.