High Precision Erase Band Measurement With Four Written Tracks

This article introduces a four track erase band width (EBW) measurement derived from triple track test. The method writes the first center track to adaptively control the track pitch (TP) and the final center track to minimize the impact from system's positioning error during EBW measurement. It uses one-way dual-frequency scan on the neighboring magnetic write width (MWW) edges to further minimize the impact from system's positioning error. Experiment shows that measured EBW decreases with TP decreasing due to the side reading, cross-track field interaction, and edge noise suppression in perpendicular recording. Setting TP at 100% MWW is proposed for measuring “intrinsic” erase band (EB). The new method demonstrates significant improvement on test accuracy over the conventional methods, and can control EBW measurement variation range within 1 nm. With the new method, the relations of EBW with write revolutions, write current, write frequency, and adjacent track interference (ATI) were experimented and analyzed. The experiment result further validates the new method.