Analysis of Adjacent Track Erasure in the HAMR Media

Abstract

Writing closely spaced tracks in the cross-track direction helps increase the storage density but leads to erasure of the adjacent tracks. This phenomenon is called adjacent track erasure (ATE). This article aims to establish the presence and numerical extent of ATE in different heat-assisted magnetic recording (HAMR) media. We find that thermal exchange coupled composite (ECC) media can be more susceptible to ATE compared with single layer FePt media of equivalent thickness. We implement optimization techniques to reduce the ATE in different media and increase the recording signal to noise ratio (SNR) in this process. While the ATE in single layer FePt media seems to be relatively impervious to changes in the applied field angle, small field angles appear to reduce the ATE for the high $T_{c}$ thermal ECC media. However, small angle also reduces the SNR, leading to the conclusion that 30° actually yields the best SNR even in the presence of overwrite. Introducing a finite intergranular exchange coupling improves the writing performance of the single layer FePt and reduces the ATE. We rigorously calculate the thermal decay constant and use it to evaluate the performance of pulsed laser recording. Finally, we establish a hypothesis that helps explain the presence of ATE in different HAMR media. We believe the ATE is proportional to the thermal stability factor at a temperature just below the write temperature. The proposed hypothesis correctly predicts the ATE in the single layer FePt media assuming coherent rotation. Our results can help increase the HAMR storage density and make HAMR media resistant to the ATE.