A study of domain noise from the soft underlayer in perpendicular media

Summary form only given. In perpendicular recording, it has long been recognized that the magnetic property of the under-layer is very important to overall performance. The soft underlayer is required to have high permeability to magnetic imaging for improved write and yet it is undesirable to have any magnetic domains in the soft layer because it creates "spike noise" during read back. Although significant research has been devoted to the study of the noise in the soft layer, no definitive solution exists. In view of the fact that much of the past study in this area was done on media designed for recording with inductive heads at much lower density (K. Sato et al., 1993; N.R. Darragh et al., 1993), a re-visit to the phenomena on media designed for GMR read/pole head write at the current areal density of interest is presented here. We used both a wide track width inductive head and merged GMR heads for this study. We were successful in studying both the static features of the domains and some dynamic features of the domain wall motion with this technique.