Structural and magnetic properties of iodide-mediated chemically synthesized L12 FePt3 nanoparticles

Vimal Deepchand,George C Hadjipanayis,Vasileios Tzitzios

doi:10.1063/9.0000102

Vimal Deepchand, George C Hadjipanayis + Show 1 more

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https://doi.org/10.1063/9.0000102

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Abstract

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.

Highlights

The structural and magnetic properties FePt nanoparticles are highly dependent on chemical composition, which can be tailored for potential applications in ultrahigh density storage media, biomedicine and catalysis
We used elemental iodine to synthesize this phase, but our results showed that the L12 FePt3 phase is obtained instead of the L10 phase
Reported work on FePt3 nanoparticles highlighted the antiferromagnetic to ferromagnetic transitions, which depend on the size and chemical ordering of the particles

Summary

Introduction

The structural and magnetic properties FePt nanoparticles are highly dependent on chemical composition, which can be tailored for potential applications in ultrahigh density storage media, biomedicine and catalysis. Most of the studies so far have been focused on equiatomic Fe-Pt with the highly anisotropic L10 structure. Recently, L10 FePt nanoparticles have been chemically synthesized through a halide mediated route without requiring any post annealing heat treatment. Strong bonds between Fe3+ and Pt2+ ions and the halide ions facilitate the formation of FePt, through an energetically favorable way, leading to the formation of an ordered state.In our experiments, we used elemental iodine to synthesize this phase, but our results showed that the L12 FePt3 phase is obtained instead of the L10 phase. The structural and magnetic properties FePt nanoparticles are highly dependent on chemical composition, which can be tailored for potential applications in ultrahigh density storage media, biomedicine and catalysis.. L10 FePt nanoparticles have been chemically synthesized through a halide mediated route without requiring any post annealing heat treatment.. FePt3 with the L12 structure is known to be paramagnetic at room temperature and shows two coexisting antiferromagnetic transitions at TN1∼160 K and TN2∼120 K.10. Reported work on FePt3 nanoparticles highlighted the antiferromagnetic to ferromagnetic transitions, which depend on the size and chemical ordering of the particles.. FePt3 nanoparticles have been shown to have an effective magnetic anisotropy energy density at least twice the value of the corresponding bulk values. FePt3 with the L12 structure is known to be paramagnetic at room temperature and shows two coexisting antiferromagnetic transitions at TN1∼160 K and TN2∼120 K.10 Previously, reported work on FePt3 nanoparticles highlighted the antiferromagnetic to ferromagnetic transitions, which depend on the size and chemical ordering of the particles. FePt3 nanoparticles have been shown to have an effective magnetic anisotropy energy density at least twice the value of the corresponding bulk values.

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