Direct one-pot synthesis of L10-FePtAg nanoparticles with uniform and very small particle sizes

If tetragonal FePt nanoparticles (NPs) are to be used as magnetic recording media, a means of transforming the particles into the tetragonal phase while maintaining the small particle size must be found. In this work, uniform and high coercivity L1(0)-FePtAg nanoparticles are successfully synthesized by a one-pot polyol-process method, using an octadecylamine solvent. Magnetic measurements show that FePtAg NPs with a high coercivity of 5.23 kOe can be achieved using the octadecylamine solvent, which is significantly higher than the NPs synthesized using hexadecylamine (2.84 kOe) and trioctylamine (2.81 kOe) solvents. STEM characterization shows that the L1(0)-FePtAg NPs synthesized in octadecylamine, with a diameter of 3.5 +/- 0.5 nm and a very uniform size distribution, are smaller in size and more uniform than those synthesized in hexadecylamine and trioctylamine solvents. The octadecylamine, hexadecylamine and trioctylamine high boiling-temperature solvents play significant roles in the morphology, structure and magnetism of FePtAg NPs, and the solvent effects on the nucleation and growth of the L1(0)-FePtAg nanoparticles are proposed. This work sheds new light on designing highly ordered L1(0)-FePt nanoparticles for ultrahigh density magnetic recording and for synthesising high performance oxygen reduction reaction catalysts.