Micromagnetics of a soft underlayer

The micromagnetic properties of a soft underlayer in perpendicular media ar e studied, It is shown that stray fields from a recording layer can substan tially modify magnetic properties of soft underlayer material, The degree o f modification is determined by the characteristic bit size in the recordin g layer and by the soft underlayer material magnetic characteristics. It is found that there exists a thin layer within a soft underlayer with re duced permeability, The effects of the presence of such a reduced permeabil ity region within a soft underlayer on both reading and writing processes a re discussed.