Structural and magnetic properties of HCP-CoCrPt-SiO₂ granular media

Granular HCP-(CoCrPt)_100-x(SiO₂)_x thin films with Cr underlayers have been fabricated by sputtering multilayers followed by post-deposition annealing. Magnetic and structural properties of the films for potential applications in magnetic recording media have been investigated in detail. In as-deposited films coercivities exceeding 2.5 kOe have been obtained with SiO₂ varying from 8 to 16 vol%; high coercivity of 5.6 kOe and anisotropy of 4.6 × 10⁶ erg/cm³ have been achieved at low M_rt value (about 0.4 memu/cm²) in the post-annealed films. VSM measurements showed that the magnetic moment lies well in the film plane under proper preparation conditions. Grain isolation in the magnetic layer was improved by segregating SiO₂ into grain boundaries and further enhanced by post-deposition annealing. The rapid increase of the coercivity upon annealing is most likely due to the significant decrease in intergranular exchange coupling, as shown by the δ M measurement in which the peak value of δ M curves changed from a positive value to a negative value upon annealing. Magnetic reversal properties of the films have also been systematically studied. These results show that the HCP-CoCrPt-SiO₂ granular film is a promising candidate for ultra-high-density recording media up to 100 Gbit/in² or beyond because of its low Pt content and desirable properties.