Study on the synthesis of NiZnCu ferrite nanoparticles by PVA sol–gel method and their magnetic properties

Ni0.65Zn0.35Cu0.1Fe1.9O4 nanoparticles fabricated by a polyvinyl alcohol (PVA) sol–gel process have been investigated by infrared spectra (IR), X-ray diffraction (XRD), transmission electron microscope (TEM) and Mössbauer spectroscopy measurements. The particles annealed at and above 250 °C are single phase NiZnCu ferrite with spinel structure. Particles annealed at and above 350 °C behave ferrimagnetically, while sample annealed at 250 °C is simultaneously paramagnetic and ferrimagnetic. In addition, the transition from the paramagnetic to the ferrimagnetic state can be observed in sample annealed at 250 °C as the measuring temperature decreases from 260 °C to liquid nitrogen temperature. The magnetic properties of NiZnCu ferrite nanoparticles are clearly size-dependent. The saturation magnetization increases with the annealing temperature. The coercivity of NiZnCu ferrite nanoparticles reaches a maximum when the annealing temperature is 550 °C.