Hydrothermal synthesis of superparamagnetic zinc–nickel ferrite nanoparticles

Zn Ni Fe nanoparticles were prepared in a three-step synthesis involving the co-precipitation of metal nano-hydroxide, coating the metal nano-hydroxide with oleic acid, and hydrothermal treatment (ferritization). The nanoparticles were analyzed using X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy. All samples heated at temperatures from 140 °C to 180 °C were crystalline Zn Ni Fe with particle sizes ranging from 5–8 nm. Vibrating sample magnetometry results indicated that the coercive force and remanence of the samples were close to zero, and the saturation magnetization values were high (14.20–27.12 emu · g ).