Adjacent and Far Track Erasure Dependence on Media Soft Underlayer Permeability in Shielded Head Recording

The permeability of the magnetic soft underlayer (SUL) was systematically varied by changing the antiferromagnetic exchange coupling, and the effect on recording performance and adjacent track erasure (ATE) and far track erasure (FTE) was investigated. Perpendicular magnetic recording performance highly depends on SUL permeability. Highly permeable SUL can reduce the head erasure field located at far tracks from a stressing track but generates more erasure at adjacent tracks near the side shield. Optimum SUL permeability can improve on-track performance with tolerable ATE or FTE. Finite element method models of a shielded write head and media with different SUL permeabilities were performed. A high-permeability SUL has a larger impact on short-time high FTE fields and potentially affects the erasure at 3-6 tracks from main pole. This shows agreement with experimental results.