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

Abstract Self-assembled face-centered cubic FePt nanoparticles were capped by a amorphous Al 2 O 3 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 °C, well-monodispersed face-centered tetragonal FePt particles can be obtained, yielding a coercivity value H c=5.9 kOe with the magnetocrystalline anisotropy of 3.86 MJ/m 3 . The thermal factor for the composite film is 68.5, meeting the industry requirement ( K u V / k B T ≥ 50). The protection of amorphous Al 2 O 3 matrix can effectively inhibit grain growth and particle aggregation, and preserve the ordered domains of FePt nanoparticles during the L 1 0 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.