Magnetic recording performance of keepered media

Using low flying and proximity inductive heads, keepered media show improved on- and off-track performance leading us to conclude that a greater than 20% areal density improvement is possible with a keeper layer over the magnetic storage layer. For Sendust keeper layers there is an optimal range of thickness and an optimal bias point for best performance. There are both amplitude and timing asymmetries that are functions of the read-back bias. For a peak detect channel the best performance corresponds to the minimum timing asymmetry although this is not the point where the pulses are narrowest. Keepered media may have an advantage in total jitter and partial erasure. NLTS is almost identical for keepered versus unkeepered media.