Effect of Dual-Magnetic-Layer on Performance of CoCrPt-SiO2 Perpendicular Media

CoCrPt-SiO₂ perpendicular recording media have been investigated in order to increase media signal-to-noise ratio (SNR) by introducing a dual-magnetic-layer structure into the CoCrPt-SiO₂ recording layer. The dual-magnetic-layer structure consists of low- and high-M_s granular layers. The magnetic properties and recording performances of two kinds of dual-magnetic-layer media, one with a low-M_s bottom layer and another with a low-M_s top layer, were measured. The coercivity of the low-M_s bottom medium is higher than that of the low-M_s top medium, although they have the same thermal stability (K_uV/k_B T). We showed that using the low-M_s bottom layer gives a higher SNR. That is to say, SNR was improved by 3 dB compared with that of the high-M_s single-magnetic-layer medium, and it was even higher than that of the low-M_s single-magnetic-layer medium. It is thus concluded that the dual-magnetic-layer structure with the low-M_s bottom layer is effective in increasing SNR of perpendicular media