Monodispersed magnetic iron-platinum and iron-platinum-X (X = silver, gold, copper, manganese) nanoparticles for ultra-high-density recording media

FePt nanoparticles are considered as a promising material for ultra-high density recording media and many other applications. As-made nanoparticles typically have the magnetically soft face centered cubic (fcc) phase. In order to transform the as-made nanoparticles to the magnetically hard face centered tetragonal (fct) phase, which is necessary for magnetic recording and permanent magnet applications, heat treatment is required.;Different size FePt and FePtX (X = Cu, Ag, Au, Mn) nanoparticles were synthesized using wet chemical procedures, and different experimental methods were used to obtain fct FePt and FePtX nanoparticles. The physical, chemical and magnetic properties of these fct FePt and FePtX nanoparticles were studied. Salt-matrix annealing was shown to be successful in preventing FePt nanoparticles from aggregation and sintering during heat treatment, and the technique allowed monodispersed fct FePt nanoparticles to be easily collected. FTIR measurements showed that the chemical bonds between the surfactant and salt-matrix are critical for holding single FePt nanoparticles firmly on the surface of salt.;Extended x-ray absorption fine structure (EXAFS) measurements were used to investigate the change of the atomic structure of FePt nanoparticles during the chemical ordering evolution at different annealing temperatures. The experimental results are consistent with calculations.