The role of soft underlayer permeability in wide area track erasure in high-density perpendicular recording

The effect of the soft underlayer (SUL) permeability on adjacent track erasure (ATE) as well as on the recording performances of the media was investigated and verified. The 3 structures used were: single layer CoZrTa, and the antiferromagnetically coupled SULs (APS) CoZrTa/Ru/CoZrTa and CoZrTa/Ru/Co/CoZrTa. All samples were deposited on NiP-plated AlMg disk substrates. The 240 tracks were written once with 45 mA at 60 kfci and the stressing track was written for 32,000 revolutions with 55 mA at 360 kfci. Similar to previous observations, the APS structure largely suppressed the ATE. It was found that the total amount of flux an SUL is capable of conducting does not correlate well with ATE. However, ATE correlates well with permeability, suggesting that material property alone determines ATE.