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A (001) textured FePt film was deposited on MoC/CrRu/glass at a substrate temperature of 380 °C by using magnetron sputtering. The MoC conductive intermediate layer was used to resist the Cr diffusion up to high deposition temperatures and promotes the epitaxial growth of the (001) textured FePt film. The FePt film showed high perpendicular magnetization and the out-of-plane coercivity increased with MoC thickness. The FePt/MoC (5 nm)/CrRu film showed a square out-of-plane magnetic hysteresis loop with a coercivity of 6.0 kOe and a linear-like in-plane loop. A multi-functional MoC intermediate layer exhibited heteroepitaxial relation with FePt and CrRu and was capable of resisting the interlayer diffusion at high deposition temperatures.

The Fe(6 nm)/FePt film with perpendicular magnetization was deposited on the glass substrate. To study the oxygen diffusion effect on the coupling of Fe/FePt bilayer, the plasma oxidation with 0.5~7% oxygen flow ratio was performed during sputtered part of Fe layer and formed the FeOx(3 nm)/Fe(3 nm)/FePt trilayer. Two-step magnetic hysteresis loops were found in trilayer with oxygen flow ratio above 1%. The magnetization in FeOxand Fe/FePt layers was decoupled. The moments in FeOxlayer were first reversed and followed by coupled Fe/FePt bilayer. The trilayer was annealed again at 500°C and 800°C for 3 minutes. When the FeOx(3 nm)/Fe(3 nm)/FePt trilayer was annealed at 500°C, the layers structure was changed to FeOx(6 nm)/FePt bilayer due to oxygen diffusion. The hard-magnetic FeOx(6 nm)/FePt film was coupled with single switching field. The FeOx/(disordered FePt) layer structure was observed with further annealing at 800°C and presented soft-magnetic loop. In summary, the coupling between soft-magnetic Fe, FeOxlayer, and hard-magnetic L10FePt layer can be controlled by the oxygen diffusion behavior, and the oxidation of Fe layer was tuned by the annealing temperature. The ordered L10FePt layer was deteriorated by oxygen and became disordered FePt when the annealed temperature was up to 800°C.