Structural and Magnetic Studies of Annealed Iron Oxide Nanoparticles

The aim of this research work was to study the structural and magnetic properties of iron oxide nanoparticles. The as-prepared sample was synthesized by a co-precipitation route and annealed at different temperatures. The annealed samples were investigated using different techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and Mössbauer spectrometry (MS). The XRD results indicate the formation of three phases which have been identified as magnetite (Fe3O4), maghemite (γ-Fe2O3), and hematite (a-Fe2O3). The crystallite size was very similar for both magnetite and maghemite, and it was higher for hematite. The TEM observations showed that the particle shapes were affected by the annealing temperature (Tan). In addition, the SEM analysis revealed a wide distribution of the particle size. The magnetic measurements enabled the determination of a blocking temperature for both Fe3O4 and γ-Fe2O3 as 210 and 240 K, respectively. The Morin transition temperature was determined in the case of α-Fe2O3 from the magnetization and the MS measurements. The synthesized iron oxide nanoparticles can be good candidates for hyperthermia applications.