Effect of soft underlayer permeability on wide area track erasure in perpendicular recording

The permeability of the magnetic soft underlayer (SUL) was systematically varied through SUL structure change, and its effect on wide area adjacent track erasure (ATE) and media overwrite (OW) was studied. Results suggest that ATE decreases with SUL permeability, and it involves only a finite thickness of the SUL. OW increases with SUL permeability as well as SUL thickness. In addition, ATE is less affected by magnetic spacing than OW. Antiparallel coupled SUL (APS) improves ATE. A double-APS structure with a permeability gradient is proposed to optimize OW and ATE performance.