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

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 ^softrang was very effective at improving the recording resolution D₅₀ due to an increase in the slope of magnetization curve alpha. The use of a Co-SiO₂ layer, which has the highest langM_s ^softrang in the present study, resulted in the highest D₅₀ 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 ^softrang and the mean value of saturation magnetization of the hard layer, langM_s ^hardrang. Moreover, it was successfully demonstrated that the magnetization reversal of (Co-Pt)-SiO₂/Co-SiO₂ stacked media changed systematically as theoretically predicted on reducing the interfacial exchange coupling by using NiFeCr-SiO₂ or Pt-SiO₂ 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 ^softrang enhanced the H_r reduction. The H_r reduction improved recording writability without degrading D₅₀, the signal to medium noise ratio SN_mR and thermal stability