EFFECT OF ANNEALING ON STRUCTURAL AND MAGNETIC PROPERTIES OF IRON OXIDE NANOPARTICLES

Nanocrystalline Fe3O4 particles were synthesized by a facile chemical route and annealed at different temperatures in argon atmosphere. The material is then characterized by X-ray diffraction technique (XRD) and dc magnetization measurements. The X-ray diffraction patterns confirm the synthesis of single crystalline phase of Fe3O4 nanoparticles. On annealing at 300 o C there is improvement in the crystal structure. A phase transition from magnetite (Fe3O4) to hematite (-Fe2O3) is observed when the samples are annealed above 500 o C. The magnetic measurements show superparamagnetic nature of the as-synthesized sample, whereas for annealed samples ferromagnetic nature is observed. The saturation magnetization decreases after phase transition.