PERPENDICULAR MAGNETIC RECORDING MEDIUM

摘要

PURPOSE:To obtain a disk-shaped perpendicular magnetic recording medium having the small modulation of a reproduction envelope by specifying the anisotropy of the reversible magnetic permeability determined from the inclination of a minor loop in the residual magnetization state of a soft magnetic layer to a specific value or below. CONSTITUTION:The anisotropy of the reversible magnetic permeability determined by the inclination of the minor loop in the residual magnetization state of the soft magnetic layer is specified to <=23% to suppress the modulation to <=3dB. The reversible magnetic permeability mur is calculated according to mur=DELTAB/DELTAH from the change DELTAH of the magnetic field and the change DELTAB of the magnetic flux density as the inclination of the minor loop. The reversible magnetic permeability sharply reflects the magnetic characteristics of the soft magnetic layer of the perpendicular magnetic recording medium having two-layered structure and the modulation is suppressed to <=3dB which is the practicable level if the ratio murh/murs between the reversible magnetic permeability murh in the direction of the axis of difficult magnetization and the reversible magnetic permeability murs in the direction of the axis of easy magnetization is <=1.23. The perpendicular magnetic recording medium having the small anisotropy in the reproduction output is thus obtd.