LAUSR

Nickel ferrite nanoparticles were synthesized by co-precipitation/hydrothermal synthesis. The synthesis temperature of the co-precipitation of the precursor was studied. At this stage, proper reaction temperature to synthesize superparamagnetic nickel ferrite nanoparticles with zero coercivity (Hc) was found to be 80 ∘C. More importantly, the effects of temperature and time of the hydrothermal process on the structural and magnetic properties of the nanoparticles were also investigated. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy were used for the structural analysis. Particle sizes and shapes were determined by transmission electron microscopy (TEM). Magnetic measurements were done by using a vibrating sample magnetometer (VSM). The particle sizes dXRD, dTEM and dVSM of nickel ferrite nanoparticles were calculated from XRD patterns, TEM images and magnetic data, respectively. By hydrothermal process, the reaction time is seen to be effective on the properties of NiFe 2O4 nanoparticles since the size of the nanoparticles and saturation magnetization (Ms) increase with the increase of the time. The effect of reaction temperature on the properties of nickel ferrite nanoparticles is also slightly observed. It is seen that the synthesized nanoparticles at 125 ∘C for 40 h exhibit a superparamagnetic behaviour (zero Hc). And Ms is found to be 50.8 emu/g which is a substantially high value. Also, the limit of superparamagnetic particle size for our study is ∼12 nm since NiFe 2O4 nanoparticles bigger than 12 nm show Hc.