Recording characteristics of CoPtCr-SiO2 perpendicular media

The recording characteristics dependence on the intermediate layer (IL) thickness is investigated for CoPtCr-SiO2 double-layered perpendicular media, which contain antiferromagnetically coupled layers (AFM) formed below soft-magnetic underlayer (SUL). With the decrease of the IL thickness from 20 to 10 nm, the signal-to-media-noise ratio (S/Nm) is slightly improved. The normalized media noise (Nm/Siso) is nearly identical although the magnetic properties, such as a coercivity, gradually deteriorate. We have calculated the bit patterns at a 480 kFCI recording density using the Landau-Lifshitz-Gilbert (LLG) micromagnetic model and found that the S/Nm gain per IL thickness (∼0.1 dB/nm) can be expected if the magnetic properties are kept the same. Adding AFM layers reduces the spike noise dramatically. The media noise at high densities, beyond the saturation (∼1000 kFCI), is 24% smaller for media having AFM layers than that of conventional-type SUL. The writing field required for suppressing the noise appearing at a low frequency is also reduced for media with AFM-SUL. Interestingly, the thermal stability of a medium with AFM-SUL is improved with a decrease in IL thickness and is −0.01 dB/decade for IL=10 nm even for a 10-nm-thick recording layer.