Comparison of media properties between hard/soft stacked composite and capping layer perpendicular recording media

The effect of soft layer thickness (tSoft) of CoTaZr–SiO2 and low Pt-containing CoCrPtO layers on media properties in hard/soft (H/S) stacked media is compared to media properties in conventional capping layer (CL) media. Coercivity and coercivity squareness in H/S stacked media continuously decrease with increasing tSoft, while they increase in CL media. H/S stacked media with CoTaZr–SiO2 layers having higher saturation magnetization and in-plane magnetic anisotropy constant exhibit stronger demagnetization effect. Compared to CL media, H/S stacked media with CoCrPtO soft layers improve signal-to-noise ratio and magnetic write width. However, the use of a relatively soft layer deteriorates adjacent track erasure and does not improve media writeability due to compensation effect between softer and harder layers to be used. These phenomena can be understood as undesirable side effects of a soft layer: higher demagnetization field and larger lattice mismatch.