Particle size dependence of magnetic features for Ni0.6−xCuxZn0.4Fe2O4 spinel nanoparticles

Ni0.6−xCuxZn0.4Fe2O4 (x=0-0.5) ferrite nanoparticles were prepared using a reverse micelle process. Micron size particles were also synthesized by a sol-gel process. Mean particle size of ferrite nanoparticles is approximately in the range of 2-10 nm as determined by X-ray diffraction (XRD), transmission electron microscopy and Langevin function. The heating thermograms of samples confirmed that there were no hydroxides in the ferrites fabricated via reverse micelles. The XRD results confirmed the formation of single phase of spinel ferrite particles for whole series of samples. The results of FTIR analysis indicated that the functional groups were formed on both nano and micron size particles. A vibrating sample magnetometer was employed to probe magnetic properties of nanosize and micron size samples. It was found that with an increase in the amount of copper in nanosize and micron size ferrites, the saturation magnetization increases. Magnetic susceptibility of nanoparticles was studied by the measurement of a.c. magnetic susceptibility versus temperature at different frequencies. The phenomenological Néel-Brown and Vogel-Fulcher models were employed to distinguish between the interacting or non-interacting system. Results exhibited that there is strong interaction between fine particles.