Figure 2. The Magnetic Hysteresis Loop of the Nanoparticles (Left) and FITR Pattern of the Silica-Coated Nanoparticles (Right).

Left, the saturation magnetization of the nanoparticles was approximately 55 emu/g, lower than the saturation magnetization of bulk magnetite (92 emu/g). Moreover, non-hysteresis and remanence phenomena were observed, which indicated an obvious superparamagnetic phenomenon that magnetism only existed when the external magnetic field was present; when the external magnetic field was removed the magnetic field completely disappears. Right, The Fe-O-Fe stretching vibration was 471/cm, and the stretching vibration of Si-O was 1104/cm. Therefore, the main peaks show that the synthetic particles contained Fe₃O₄ and silica.