CoPtCr-SiO₂ granular media for high-density perpendicular recording

SiO₂ added CoPtCr magnetic layers are employed for perpendicular recording media. The microstructure, magnetic properties, and recording performance of these media are discussed. Very fine grains with size of less than 7 nm, surrounded by grain boundaries mainly consisting of silicon oxide, are realized. The addition of SiO₂ to CoPtCr is very effective in enhancing the well-isolated fine grain structure without disturbing the epitaxial growth of the CoPtCr grains on the Ru underlayer. The media show a large perpendicular anisotropy K_u of ∼4 × 10⁶ erg/cm³ and a K_uV/kT value of more than 80, even at a CoPtCr-SiO₂ thickness of 12 nm, resulting in a high coercivity H_c (∼4 kOe) and high squareness M_r/M_s of ∼0.96. The CoPtCr-SiO₂ medium shows excellent signal-to-medium-noise ratio performance together with high thermal stability at very thin thickness, indicating great potential for high-density perpendicular recording media.