Ultrasound-Assisted Synthesis and Tuning the Magnetic and Structural Features of Superparamagnetic Fe₃O₄ Nanoparticles by Using Ethylenediamine as a Precipitating Agent

Due to the strong effect of nanoparticles' size on the magnetic and structural properties of Fe₃O₄ (magnetite) nanoparticles, the size selection proportional to desired magnetization especially superparamagnetic characteristic of these particles is very important. In this work, at first, the Fe₃O₄ nanoparticles successfully synthesized by a novel precipitating agent, ethylenediamine (EN), with an ultrasonic treatment (40 kHz, 150 W) by the co-precipitation method. Then, in order to accurately investigate the synthesis conditions on the physical properties of Fe₃O₄, the influence of reaction temperature, reaction time, and precipitating agent are studied. The structural and magnetic properties of the as-prepared nanoparticles are characterized by X-ray diffraction (XRD), Rietveld refinement, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) analysis. It is found that the EN produces magnetite nanoparticles with a larger size and desired saturation magnetization (M_s). The absence of impurity phases in all of the synthesized nanoparticles and formation of the spinel structures at low temperature (30 °C) can be due to the influence of the ultrasound waves.