Size control synthesis and high coercivity L10-FePt nanoparticles produced by iron (III) acetylacetonate salt

Halide Ion-Mediated Synthesis of L10-FePt Nanoparticles with Tunable Magnetic Properties

L1₀-FePt nanoparticles (NPs) have great potential in areas of advanced magnetic and catalytic applications. Here, we present a facile control route for synthesis of hard magnetic L1₀-FePt NPs in which halide ions (Cl^-, Br^-, or I^-) were added to the synthetic process to promote the phase transformation. It is confirmed that the strong ionic binding force between halide ions and Fe³⁺ or Pt²⁺ ions could facilitate the formation of L1₀-FePt phase due to favoring growth of FePt NPs in a more thermodynamically stable way, which enables the formation of an ordered structure. L1₀-FePt NPs with the highest coercivity of 8.64 kOe and saturation magnetization of 64.21 emu/g at room temperature can be directly obtained by controlling the amount of the halide ions. In comparison with conventional solution phase reduction methods, the halide ion-assisted method shows enhanced capability to tune the growth of hard magnetic bimetallic NPs, particularly Pt-based bimetallic NPs.

A general strategy for synthesizing high-coercivity L10-FePt nanoparticles

It is extremely desirable but challenging to develop a facile solution phase synthesis to directly prepare well-dispersed L1₀-FePt nanoparticles (NPs) to meet the requirements of advanced magnets in modern industry and information technology. Here, we report a novel strategy to synthesize hard magnetic L1₀-FePt NPs via controlled co-reduction of Fe(acac)₃ and K₂PtCl₆ in the presence of oleylamine, in which effective control of the magnetic properties and chemical ordering of L1₀-FePt NPs was achieved by tuning the mole ratio of the precursors, reaction time and temperature. The highest coercivity of 10.5 kOe can be obtained for the NPs synthesized at 350 °C for 8 h, which is much higher than the coercivities reported by the previous studies on solution-synthesized FePt NPs without annealing or the third elemental additive. The reported one-pot synthesis of L1₀-FePt NPs may provide an ideal class of building blocks for magnetic energy applications.