Investigation of the Influence of Annealing Temperature on the Structural and Magnetic Properties of MgFe₂O₄

In this paper, nanocrystalline Mg-ferrites have been synthesized by the low-cost sol-gel auto-combustion method using iron and magnesium nitrates as starting materials. The as-prepared sample was annealed at temperatures of 200°C, 400°C, 600°C, 800°C, and 1000°C in an air atmosphere to investigate the effect of annealing temperature on the physical properties. The structural and magnetic properties of the annealed ferrites were studied using x-ray diffraction, Fourier transform infrared (FTIR) and Raman spectroscopy, and vibrating-sample magnetometer. The crystalline size of the nano-crystallites increased from 12 nm to 51 nm with an increase in annealing temperature from 200°C to 1000°C. Raman spectroscopy measurements revealed the presence of a spinel structure where A_1g and E_g modes occur along different bond lengths of Fe/Mg-O, due to different ionic radii of Mg⁺² and Fe⁺³ ions. The two prominent vibration frequency peaks along different bond lengths for the cubic spinel materials were confirmed using the FTIR spectra. The saturation magnetization was found to increase from 0.71 μ_B/f.u. to 1.16 μ_B/f.u. with increasing annealing temperature from 200°C to 1000°C. The magnetization results show that the magnetic properties of the nanocrystalline Mg-ferrites improved with annealing temperature.