Microstructure and Superparamagnetic Properties of Mg-Ni-Cd Ferrites Nanoparticles

Magnesium substituted nickel cadmium ferrite nanoparticles MgxNi0.6-xCd0.4Fe2O4 (from x = 0 to 0.6 with step 0.1) have been synthesized by the chemical coprecipitation route. X-ray diffraction (XRD) and infrared spectroscopy (FTIR) revealed that the obtained powders have a single phase of cubic spinel structure. The crystallite sizes calculated from XRD data have been confirmed using transmission electron microscopy (TEM) showing that the powders are consisting of nanosized grains with an average size range 5-1.5 nm. Magnetic hysteresis loops were traced at 6.5 K as well as at room temperature using VSM. It was found that, due to the Mg2+-ions substitution, the values of saturation magnetization M-s for the investigated samples were decreased, whereas the coercive field H-c increased. Both zero field cooling (ZFC) and field cooling (FC) curves are measured in the temperature range (6.5-350 K) and the values of blocking temperature T-B were determined. No considerable variation in the values of T-B was observed with increasing Mg-content, whereas the values of the effective anisotropy constant K-eff were increased.