Abstract
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.
Highlights
Equiatomic FePt film with anisotropic face-centered tetragonal L10 ordered structure has high magnetocrystalline anisotropy which is the promised material in energy assisted perpendicular magnetic recording
7%, respectively The shoulders appearing in the loops in Figures 3(d)–3(f) disappeared after further annealing. and the loops present single magnetization reversal process. It suggested that the Fe layer was further oxidative, and the layer structure was changed to exchange coupled FeOx/FePt film
The plasma oxidation was performed during sputtered part of Fe layer in Fe/FePt film and formed the FeOx(3 nm)/ Fe(3 nm)/FePt trilayer
Summary
Equiatomic FePt film with anisotropic face-centered tetragonal (fct) L10 ordered structure has high magnetocrystalline anisotropy which is the promised material in energy assisted perpendicular magnetic recording. The L10 FePt phase was ordered from disordered FePt phase with face-centered cubic (fcc) structure after high temperature annealing [1,2,3,4,5,6]. The granular structure with columnar grains [7, 8] and well c-axis alignment normal to the film surface with low switching field distribution are required for FePt perpendicular recording media. It is necessary to have high [001] textured FePt granular film with lower coercivity that was accepted by writing temperature and field. The [001] textured FeOx/FePt dewetted film with perpendicular magnetization was observed
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