Alternating Magnetic Field and Ultrasound Waves as Size Controlling Parameters in Preparation of Superparamagnetic Fe₃O₄ Nanoparticles.

Magnetic nanoparticles have been studied extensively owing to their widespread applications. Here, a novel and simple co-precipitation method is introduced in the presence of an external alternating magnetic field along with ultrasound waves for the synthesis of uniform magnetite (Fe3O4) nanoparticles with an average particle size of below 10 nm, the results of which were compared further. These agitating probes were employed to induce nucleation process of Fe3O4 nanoparticles resulting in creation of such particles with remarkable magnetic properties. These were assessed by XRD, TEM, vibrating sample magnetometer (VSM), AFM, and magnetic force microscopy (MFM) analyses. XRD patterns revealed the spinel phase of the obtained magnetite. The size and morphology of the nanoparticles were determined by AFM, TEM, and HR-TEM. The results indicated efficient control over size distribution in such new processes. The magnetic properties of the prepared Fe3O4 nanoparticles were characterized by MFM and VSM, demonstrating their superparamagnetic behavior. They showed saturation magnetization ranging from 57.4 to 79.4 emu/g with coercivity of 11.9 to 12.55 Oe, depending on the applied procedure.