Recording Resolution and Writability for (Co-Pt)-SiO$_{2}$/Co-SiO $_{2}$ Hard/Soft-Stacked Granular Perpendicular Media

The magnetic properties and recording performance of hard/soft stacked media consisting of a magnetically hard 9-nm-thick (Co-Pt)-SiO
₂
layer underneath a thin (2-3 nm) soft granular layer were studied. Experimental results indicated that an increase in the mean value of saturation magnetization of the soft layer langM
_s

^soft
rang was very effective at improving the recording resolution D
₅₀
due to an increase in the slope of magnetization curve alpha. The use of a Co-SiO
₂
layer, which has the highest langM
_s

^soft
rang in the present study, resulted in the highest D
₅₀
value. It is likely that the increase in alpha was mainly caused by the demagnetization field in grains due to the difference between langM
_s

^soft
rang and the mean value of saturation magnetization of the hard layer, langM
_s

^hard
rang. Moreover, it was successfully demonstrated that the magnetization reversal of (Co-Pt)-SiO
₂
/Co-SiO
₂
stacked media changed systematically as theoretically predicted on reducing the interfacial exchange coupling by using NiFeCr-SiO
₂
or Pt-SiO
₂
interlayers. The reduction of remanence coercivity H
_r
was achieved by controlling the thickness and film composition of the interlayer, moreover, a high-langM
_s

^soft
rang enhanced the H
_r
reduction. The H
_r
reduction improved recording writability without degrading D
₅₀
, the signal to medium noise ratio SN
_m
R and thermal stability