Microemulsion synthesis and magnetic properties of FexNi(1−x) alloy nanoparticles

• FexNi(1−x) alloy NPs synthesized by simultaneous metal ions reduction in microemulsion.
• Finer NPs synthesized at lower amount of oil and water and higher amount of CTAB.
• Chain-like FexNi(1−x) NPs are ferromagnetic; higher aspect ratio, more magnetization.
• Spherical FexNi(1−x) NPs with smaller size (7 nm) are superparamagnetic.
• Spherical FexNi(1−x) nanoparticles with higher x had increased magnetic properties.

This paper investigates synthesis of FexNi(1−x) bimetallic nanoparticles by microemulsion method. Through studying the mechanism of nanoparticles formation, it is indicated that synthesis of nanoparticles took placed by simultaneous reduction of metal ions and so nanoparticles structure is homogeneous alloy. FexNi(1−x) nanoparticles with different sizes, morphologies and compositions were synthesized by changing the microemulsion parameters such as water/surfactant/oil ratio, presence of co-surfactant and NiCl2·6H2O to FeCl2·4H2O molar ratio. Synthesized nanoparticles were characterized by transmission electron microscopy, particle size analysis, X-ray diffraction, atomic absorption and thermogravimetric analyses. The results indicated that, presence of butanol as co-surfactant led to chain-like arrangement of nanoparticles. Also, finer nanoparticles were synthesized by decreasing the amount of oil and water and increasing the amount of CTAB. The results of vibrating sample magnetometer suggested that magnetic properties of FexNi(1−x) alloy nanoparticles were affected by composition, size and morphology of the particles. Spherical and chain-like FexNi(1−x) alloy nanoparticles were superparamagnetic and ferromagnetic, respectively. Furthermore, higher iron in the composition of nanoparticles increases the magnetic properties.

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