Fabrication and magnetic properties of FePt/Al₂O₃ composite film by atomic-layer-deposition

Self-assembled face-centered cubic FePt nanoparticles were capped by a amorphous Al₂O₃ capping layer with the thickness of 10 nm using the atomic layer deposition (ALD) technology, and transmission electron microscopy indicates that the FePt nanocrystals are well-separated. After annealing the composite film at 700 1C, well-monodispersed face-centered tetragonal FePt particles can be obtained, yielding a coercivity value Hc=5.9 kOe with the magnetocrystalline anisotropy of 3.86 MJ/m³. The thermal factor for the composite film is 68.5, meeting the industry requirement (K _uV/k_BT ≥ 50). The protection of amorphous Al ₂O₃ matrix can effectively inhibit grain growth and particle aggregation, and preserve the ordered domains of FePt nanoparticles during the L1₀ ordering transition. The combination of ALD-capping layer and self-assembled FePt nanoparticles provides a new potential approach to fabricate patterned magnetic recording media with ultrahigh areal density.