Effect of continuous layer in CGC perpendicular recording media

Abstract

The effect of continuous layer on CoCrPt–SiO 2 granular layer is studied in coupled granular continuous (CGC) perpendicular recording media. In the cross-section transmission electron microscope (TEM) observation, magnetic grain in the granular layer shows columnar structure, while Co/Pd multilayer shows continuous layer. The plane-view TEM image of the granular layer shows well-isolated grain structure with average grain size of around 6 nm, and grain-to-grain separation width of around 2 nm. Therefore, the interactions among the grains are negligible ( J∼0). By depositing a continuous layer on a CoCrPt–SiO 2 granular layer, the grains in the granular layer are magnetically coupled through capping layer that leads to the suppression of magnetic anisotropy dispersion. This CGC structure reduces the coercivity dispersion ( Δ H c / H c ) from 0.26 to 0.15 and saturation field ( H s) from 10.4 to 6.7 kOe. The reduction of H s and Δ H c / H c improves the OW by 21.3 dB. The small Δ H c / H c also maintains SNR of CGC media with strong magnetic exchange coupling. Furthermore, the coupling of grains through continuous layer enlarges the magnetic nucleation field ( H n) from 0.4 to −1.7 kOe. Consequently, CGC media shows better thermal stability compared to non-CGC media.