Successful fabrication of high K _u columnar CoPt-SiO₂ granular film sputtered under high substrate temperature

High substrate temperature sputtered CoPt-SiO₂ granular films with columnar grain structure, high perpendicular uniaxial magnetic anisotropy (K_u⊥), and low stacking faults (SFs) are reported. By introducing a CoCr-SiO₂ buffer layer onto a Ru layer, SiO ₂ segregates to Ru grains boundaries and CoCr grains grow epitaxially onto Ru grains. Consequently, the bumpy surface morphology of the underlayer is maintained even though the temperature of the substrate heating is subsequently elevated to around 400°C. Therefore, the CoPtCr magnetic grains of the CoPtCr-SiO₂ granular recording layer can grow epitaxially with columnar structure upon the CoCr grains of the CoCr-SiO₂ buffer layer. For deposition of CoPt-SiO₂ (no Cr) granular films at the substrate temperature below 400°C, the increase of SFs can be suppressed such that K_u⊥ can be kept high at around 6.5×10 ⁶ergs/cm³ (K_u^grain of around 9.0×10⁶ergs/cm³, where K_u^grain is referred to uniaxial magneto-crystalline anisotropy of the magnetic grains when oxide material is excluded from the granular layer).