Probing the structural and magnetic properties of small crystalline nickel ferrite nanoparticles near the upper size limit of the single-domain regime

Abstract

ABSTRACTNickel ferrite nanocrystalline particles were prepared by hydrothermal method. A systematic study was carried out on their structural and magnetic properties in wide ranges of temperatures and magnetic fields. The prepared nanoparticles were investigated by XRD, TEM, FTIR, and VSM. The results of Rietveld refinement revealed that the nanoparticles have a cubic single phase spinel type structure. The TEM measurements showed that the nanoparticles were monodisperse and spherical in shape. The FTIR results confirmed the single phase nature of the prepared nanoparticles. The magnetic measurements showed that the nanoparticles were ferromagnetic over a wide temperature range. The saturation magnetisation and the first anisotropy constant were observed to increase with reducing temperature. The estimated size of a single magnetic domain was found to be around 13 nm, which is three times smaller than the estimated crystallite size found from XRD, confirming that the average size of the nanoparticles was located above the critical size of the single-domain regime.