Structure, Optical, and Magnetic Properties of Magnetite Nanoparticles Doped with Zinc and Lanthanum and Prepared in Oxygen and Nitrogen Atmosphere

A comparative study of structural and magnetic properties for the Zn2+ and La3+ ions co-doped magnetite nanoparticles of the general formula [(1-x)Fe3O4:Zn:xLa, where x = 0.0, 0.1, 0.15, 0.2, 0.25, and 0.3] was prepared via co-precipitation method under oxygen and nitrogen atmosphere. The stoichiometric ratios of the elements in the given general formula were proved and confirmed by both Inductively coupled plasma (ICP) measurements and atomic absorption data. Various analytical and characterization techniques were used to analyze the prepared nanoparticles. X-ray diffraction (XRD) confirmed the formation of one single phase of nanoparticles components with average crystalline size ranging from 6 nm to 9 nm at oxygen atmosphere and from 6 nm to 8 nm at nitrogen atmosphere. These size values were calculated by Debye-Scherrer equation. The morphology of Zn2+ and La3+ ions co-doped magnetite nanoparticles was studied using field-emission scanning electron microscope (FE-SEM) and high-resolution transmission electron microscope (HR-TEM). Optical properties were demonstrated by UV-visible-NIR spectrophotometer. The high absorbance values of ZnLa(x)Fe(3-x)O4 were found to be 80–97% and 80–99% in the visible wavelength range of 400–800 nm for the prepared samples in the presence of O2 and N2 gases at room temperature, respectively; which proved the lower values of energy bandgap in both conditions. The lowering of energy bandgap of 1.89 eV for nanoparticles prepared in O2 gas and 1.78 eV for those prepared in N2 gas in most samples may be attributed to incorporation of Zn cation. Magnetic properties of the given samples, obtained from vibrating sample magnetometer (VSM), showed that most of these samples exhibited almost superparamagnetic behavior. These magnetic values (32.87 emu/g and 24.79 emu/g) infer super saturation magnetization of the given samples prepared in O2 and N2 gases at room temperature, respectively. Examination of the magnetic properties revealed decrease in saturation magnetization with increasing La ion concentrations incorporation up to x = 0.3.