Low-Temperature Sol–Gel Autocombustion Synthesis and Magnetic Properties of Magnetite

Using citric acid, ferric nitrate, and ammonia as starting materials, magnetite (Fe₃O₄) powders were successfully synthesized through a low-temperature sol-gel autocombustion method. The molar ratios Φ of citric acid to ferric nitrate were adjusted from 0.1:1 to 1.5:1. The combustions were activated at a temperature as low as 300 °C. The X-ray diffraction was used in the determination of the phases of the prepared samples. The results illustrate that some of the as-prepared samples have pure Fe₃O₄ phase. Magnetite can be synthesized within a large range of molar ratio of citric acid to ferric nitrate. Scanning electron microscopy studies show us porous characteristics of the prepared samples. The results of vibrating sample magnetometer studies show us ferrimagnetic properties of the as-prepared magnetite products at room temperature with a maximum saturation magnetization as high as 91 emu/g. The magnetic hysteresis loops reveal soft magnetic properties of these materials. The saturation magnetization value of the sample of Φ = 0.5 is about 99% of the corresponding bulk value, which indicates that Φ = 0.5 is the most suitable molar ratio for the experiment.