The effect of sintering temperature on evolution of structural and magnetic properties of nanostructured Ni0.3Zn0.7Fe2O4 ferrite

Nanocrystalline Ni0.3Zn0.7Fe2O4 ferrite was synthesized by the sol–gel auto-combustion method. The structural, morphological, and magnetic properties of samples, sintered at different temperatures of 350–1,200 °C, have been studied using X-ray diffraction (XRD), field emission scanning electron microscope, Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometer (VSM), and AC susceptibility. XRD results indicated that the average crystallite sizes are in the range of ∼13 to ∼58 nm. The activation energy of crystallization of Ni0.3Zn0.7Fe2O4 ferrite was found to be 12.46 kJ mol−1. Also, the spinel phase formation was further monitored by the FTIR analysis. VSM studies of the samples indicate that magnetization increases with the crystallite size and the maximum magnetization (49.42 emu g−1) observed in the sample sintered at 1,200 °C. The coercivity increases with increasing the crystallite size and reaches a maximum value of 13.82 Oe, then decreases. Also, the low temperature-sintered samples (350 and 400 °C) were superparamagnetic, due to their near-zero coercivity and remanence. AC susceptibility measurements on low temperature-sintered samples show that the interparticle interaction leads to the superspin glass-like behavior in these nanoparticle samples