Structural, magnetic, and optical properties of nano-sized Ni<inf>0.85</inf>Se

Abstract

Nanocrystalline Ni0.85Se was synthesized by a hydrothermal method. X-ray diffraction analysis by Rietveld method indicated that Ni0.85Se has a NiAs-type hexagonal structure. Narrow crystallite size distribution with an average area-weighted size of 〈ɛF〉 = 8.5 nm is obtained by Warren-Averbach method. Structural analysis revealed deformed Se atoms octahedron with the shortest distance between Se atoms in adjacent planes 〈Se–Se〉adj smaller than between nearest neighbors in layer plane 〈Se–Se〉nea, and a rather short interatomic distance between the transition metal atoms 〈Ni–Ni〉. The optical property of Ni0.85Se was studied by UV-spectroscopy. Magnetic measurement shows a ferromagnetic phase transition for Ni0.85Se below 14 K.