Abstract: The hexagonal close-packed Ni nanoparticles were synthesized with the precursor prepared by sol-gel method via heat-treating technique in Ar atmosphere. The synthesis condition, structural and magnetic properties of the samples were analysed by means of thermogravimetric analysis (TG), different thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The results indicate that hcp Ni nanoparticles with spheric shape were synthesized by heating precursor at 300 ℃. The average grain size of the hcp Ni particles is evaluated to be about 12 nm via Scherrer equation. The RT magnetic measurement in 800 kA/m field for the samples suggests the unsaturated magnetization in hcp nanoparticles. It turns out that the hcp Ni nanoparticles have unique ferromagnetic with a magnetization of 0.58 (A·m2)/kg and a coercivity of 1.592 kA/m. The critical size of superparamagnetic behavior is near to 12 nm.

Key words: sol\|gel, Ni nanoparticles, hexagonal close\|packed, ferromagnetic behavior