Co-Pt nano-composite perpendicular magnetic recording media aiming at 500 Gbit/in^2 and beyond

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A Co-Pt-oxide film for high density magnetic recording media is proposed aiming at 500 Gbit/in^2 and beyond. The media are required to posses many characteristics such as (a) nano-composite structure with magnetically isolated grain structure for low noise property, (b) nano-size crystal grains with uniform size distribution for high resolution and (c) large magnetic anisotropy energy for thermal stability of the recorded bits. Some ideas for resolving the requirements are proposed as listed below, (1) a Co-Pt film with large magnetic anisotropy energy is adopted for storage layer, (2) a composite structure of the Co-Pt film with an oxide material is used and a TiO_2 is proposed as a superior oxide material and (3) a stacked structure with high Ar gas pressure deposited Co-Pt film and Co-Pt-TiO_2 with magnetically isolated structure is proposed.A large magnetic anisotropy of the Co-Pt film was obtained by optimizing deposition conditions for the Co-Pt and also under layers. Further magnetically isolated structure was pursued by compositing the film with oxides. Gibbs free energy of the oxides was used to choose a suitable oxide for the composite film. A TtO_2 material was found to form almost stoichiometric composition in the composite film from the beginning of the Co-Pt-TiO_2 layer growth compared with other oxide added Co-Pt films. This film has a relatively low M-H loop slope which expects low noise property of the medium. Co-Pt-TiO_2 shows an average grain size and very small distribution of 6.4 nm and 15 %, respectively.A stacked structure of the nano-composite Co-Pt-TiO_2 film followed by the exchange coupled Co-Pt film is proposed for the candidate structure of the next generation high density media. Magnetic properties such as an M-H loop slope and perpendicular coercivity can be controlled by Ar gas pressure of the Co-Pt layer deposition.