Crystallographic structures and magnetic properties of L 1 o-type FePt nanoparticle monolayered films stabilized on functionalized surfaces

Crystallographic structures and magnetic properties of chemically synthesized FePt nanoparticles, which were firmly stabilized into a monolayer on thermally oxidized Si substrate using 3-amino propyldimethylethoxysilene, were studied. The two-dimensional structure of FePt nanoparticles was confirmed by plan-view high-resolution scanning microscopy observation. The particles transformed from fcc to highly ordered Li0 structure by annealing at 800DGC under high vacuum with minimal coalescence. From rotational hysteresis loss analysis, a large magnetic anisotropy field of over 8OkOe for the 800DGC-annealed film was estimated. The coercivity of the annealed sample was very small and of the order of 10(2) Oe at room temperature, meanwhile, the remanence coercivity obtained from DC demagnetization measurement was over 11 kOe. This large difference was resulted from the co-existence of Fe-poor particles with different low anisotropy fields in the monolayered film.