Improved synthesis and easy-axis alignment of L1-FePt nanoparticles

A synthesis of partially ordered FePt nanoparticles has been developed. It involves the simultaneous reduction of iron acetate (or iron chloride) and platinum acetylacetonate. The high boiling point chemical hexadecylamine or trioctylamine was used as a solvent, and oleic acid or 1-adamantanecarboxylic acid was used as a surfactant. The reflux temperature of the mixture solutions ranged from 330to360°C, where disordered FePt particles can be partially transformed into the ordered L10 phase. Compared with previous results, x-ray-diffraction patterns of as-made samples prepared with the synthesis show a higher degree of chemical ordering. The composition of the FePt nanoparticles with the synthesis can be easily tuned. The room-temperature coercivity of as-made samples ranged from 1to4kOe, depending on the particle composition as well as the refluxing temperature during synthesis. The as-made particles were aligned in a 10kOe magnetic field, giving a parallel to perpendicular remanence ratio of about 1.6.