Magnetic Properties and Corrosion Resistance Studies on Hybrid Magnetic Overcoats for Perpendicular Recording Media

Magnetic properties and corrosion inhibition properties of hybrid magnetic overcoats (Hy-MOC) that are suitable for ultra-high-density recording are investigated. Two types of Hy-MOC using different types of Co-based alloys were investigated for the magnetic overcoat (MOC). Hy-MOC(alpha) used CoCrPt : SiO2 (14% SiO2) while Hy-MOC(beta) used CoCr22 as the sputtering targets for the reactive sputtering with N-2. Magnetic hysteresis loops indicated that both types of Hy-MOC-using various percentages of N-2 flow rate-are coupled with the recording layers of the hard disk media. Hy-MOC also increased the coercivity of the perpendicular media which is attributed to the enhanced thermal stability. It was also found that the remanent squareness (S = M-r/M-s) of the media using the MOC was closer to 1. The negative nucleation field (H-n) of the media using Hy-MOC(alpha) also showed a slight increase as compared to the medium without Hy-MOC but it is not seen for the media using Hy-MOC(beta). Potentiodynamic polarization analysis of Hy-MOC samples also indicated that the Hy-MOC are able to provide sufficient corrosion protection for the hard disk media; and they are as good or even better than 2 nm amorphous carbon overcoat.