Crystalline zinc ferrite (ZnFe2O4) was prepared by the thermal treatment method, followed by calcination at various temperatures from 723 to 873 K. Poly (vinyl pyrrolidon) (PVP) was used as a capping agent to stabilize the particles and prevent them from agglomeration. The characterization studies were conducted by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The average particle sizes of 1731 nm were obtained by TEM images, which were in good agreement with the XRD results. Fourier transform infrared spectroscopy (FT-IR) confirmed the presence of metal oxide bands at all temperatures and the absence of organic bands at 873 K. The magnetic properties were demonstrated by a vibrating sample magnetometer (VSM), which displayed super paramagnetic behaviors for the calcined samples. The present study also substantiated that, in ferrites, the values of the quantities that were acquired by VSM, such as the saturation magnetization and coercivity field, are primarily dependent on the methods of preparation of the ferrites. Electron paramagnetic resonance (EPR) spectroscopy showed the existence of unpaired electrons and measured the peak-to-peak line width (Δ Hpp), the resonant magnetic field (Hr), and the gfactor values.

Nickel ferrite nanocrystals were prepared from an aqueous solution containing metal nitrates and poly (vinyl pyrrolidone) (PVP) as a capping agent. To stabilize the particles, they were thermally treated at various temperatures from 623 to 823. K at which calcination occurred, thereby stabilizing the particles, controlling the growth of the nanoparticles, preventing their agglomeration, and creating a uniform distribution of particle sizes. The characterization studies were conducted by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). The crystallization was completed between 723 and 823. K, as revealed by the absence of organic absorption bands in the FT-IR spectra Magnetization measurements were obtained at room temperature by using a vibrating sample magnetometer (VSM), which showed that the calcined samples exhibited ferromagnetic behaviors. Finally, we used TEM images and FT-IR spectra to investigate the same process in the absence of PVP and with various of concentrations of PVP for comparison with the results acquired from using the optimum concentration that was used in this work.

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