In-plane component reduction and Ku enhancement of FePt-oxide granular films by using (Pt, Ag)-C/ FePtCu-C stacked granular buffer layers

Investigation of nanostructure and magnetic properties of the granular films deposited on stacked buffer layers (BLs) of (Pt, Ag)-C/ FePtCu-C is reported. By optimizing film thickness of the (Pt, Ag)-C/ FePtCu-C BLs, uniaxial magneto-crystalline anisotropy energy (K_u⊥^film) of 2.7×10⁷ erg/cm³ was achieved for the Pt-C/FePtCu-C BLs and 2.2×10⁷ erg/cm³ for the Ag-C/ FePtCu-C BLs. In addition, the amount of magnetic grain with c-axes parallel to the film plane of those granular films is suppressed. Furthermore, FePt grain size of the granular film deposited on Ag-C/ FePtCu-C BLs is smaller than that of deposited on Pt-C/ FePtCu-C BLs. Therefore, the stacked BLs combining (Pt, Ag)-C and FePtCu-C BL satisfy both the requirements for low in-plane (001) components and high K_u⊥^film. (Pt, Ag)-C/ FePtCu-C stacked BLs are useful for extending high recording density in HAMR application.