This work focuses on the study of the magnetic and structural properties of chemically synthesized FePt1-xNix nanoparticles, with Ni content x in the range 0.2-0.4. We report the effect of Ni substitution on the L10 structure, on both the as-synthesized and annealed nanoparticles. A decrease in nanoparticle size as well as in chemical order is observed with an increase in Ni content, for both the as-made and annealed nanoparticles. The results also show that the post annealing procedure at 700oC significantly enhanced the L10 ordering of the nanoparticles. Substitution of nickel leads to a decrease in coercivity from 14.9 kOe in FePt to 0.8 kOe for FePt0.6Ni0.4 alloy, while the magnetization at 3 T is increased from 48 emu/g to 88 emu/g.

In this work, we study the effect of elemental iodine as a halide intermediary in the synthesis of FePt3 nanoparticles using a co-reduction of Fe(acac)3 and (NH4)2PtCl2 with 1,2-hexadecanediol. Our study shows that elemental iodine facilitates the formation of FePt3 nanoparticles with the L12 structure. When iodine is not used, the as-made nanoparticles have mostly the disordered fcc FePt3 structure. The as-made nanoparticles are ferromagnetic and have a Curie temperature close to 380 K. Annealing of the as-made nanoparticles leads to an increased particle size and a transformation to the ordered L12 FePt3 phase. Nanoparticles annealed at 700°C for 30 minutes show a mixture of two magnetic phases, a ferromagnetic phase with a lower ordering temperature of ∼300 K and an antiferromagnetic phase with a Néel temperature around 135 K.