Writer flux closure, transition degradation mechanism, and frequency dependent side track erasure in perpendicular recording

In this second part of the work, the MAGPAR micromagnetic/finite element model was reused to investigate the physics of the write and erase processes in perpendicular recording. The damping constant needed in the Landav–Lifshitz–Gilbert equation was found by applying the Klaassen nonlinear eddy current damped model and set to be 0.1. Previous work highlighted the fact that domains were formed in the soft magnetic underlayer (SUL) under the writer pole in regions where the field opposes the SUL magnetization direction. The domains participate in flux closure and help a more linear response out of the return pole that enhanced fields with an overshoot and opposite polarity relative to the main pole field. These return pole fields could cause adjacent track erasure and MAGPAR was used to study the physics behind it. Particular attention was given to the analysis of frequency or time dependent effects caused by flux delays from the slow moving SUL domains (between the main and return poles). In contrast, fast...