Regular Arrangement of Gas Phase Prepared In-Flight Annealed FePt Nanoparticles on S Layers

To achieve a regular quadratic particle arrangement, gas phase prepared FePt nanoparticles which were annealed in flight in order to obtain the highly anisotropic tetragonal L1₀ structure are deposited onto the regular 2-D bacterial surface-protein layer (S layer) of Bacillus sphaericus NCTC 9602 which exhibits a four-fold lattice symmetry with a lattice constant of 12.5 nm. The degree of regularity is studied by the statistical evaluation of the particles positions observed by transmission electron microscopy. Although the obtained regularity for the annealed hard magnetic particles is less than for previously studied disordered fcc FePt nanoparticles, a template-directed transfer of both lattice symmetry and periodicity from the 2-D protein crystal to the particle arrangement is observed. In addition, particle agglomeration which has been shown to have a strong effect on the arrangement´s regularity, is clearly reduced for the annealed particles because of the mutual magnetic repulsion of adjacent particles.