A Study of Nonlinear Partial Erasure Versus Frequency and Side Track Erasure in a Modern Perpendicular Magnetic Recording System

The following study examines nonlinear signal losses in a perpendicular magnetic recording (PMR) system using tunneling magneto-resistive heads (TuMR) and exchange coupled multi-layered media capable of operating at recording density greater than 400 GB/in². This study differs from previous total nonlinear distortion (TNLD) and nonlinear transition shift (NLTS) studies in that it focuses on nonlinear partial erasure (NLPE) using constant tones. Constant-tone NLPE is often considered negligible compared to pattern-dependent NLTS, but this study shows this is not the case at high linear densities. This study will further show that NLPE behavior at low linear density appears similar when using high density writes combined with track edge trimming. This novel finding suggests on-track NLPE and cross-track data width may simply be different aspects of track edge curvature and/or percolation.