Biologically derived nanomagnets in self-organized patterned media

Chemically synthesized high-anisotropy magnetic nanoparticles have demonstrated thermal stability and extremely narrow size distributions that are critical for reducing noise in future media applications. Due to their monodispersity, they also exhibit emergent self-patterning that could potentially support bit-per-particle densities up to 2 to 8 Tb/cm² (10 to 50 Tb/in²). The authors report on the challenges and progress in developing self-organized nanoparticle arrays for magnetic recording at densities up to and beyond 30 Gb/cm² (200 Gb/in ²), and in particular describe the beneficial use of biological templates in developing such media. CoPt grains are prepared within monodisperse protein spheres from aqueous reactants, with synthesis conditions controlling grain size, structure, and composition. Dispersions of these protein-encapsulated grains can be induced to form patterned precursor films that retain long range order irrespective of a distribution in grain size. Assemblies are annealed to form films of L1₀ phase nanomagnets within carbonized shells that can support stable transitions up to 1 Gb/cm² (6 Gb/in²).