Microstructure and Magnetic Properties of Iron Oxide Nanoparticles Prepared by Wet Chemical Method

Abstract

The magnetic properties of iron oxide nanoparticles prepared by the chemical decomposition of the iron chlorides with the ratio Fe 3+ /Fe 2+ = 2.25 were studied by means of transmission electron microscopy, X-ray diffraction and Mössbauer spectroscopy in-and without external magnetic field.The transmission electron microscopy studies show that the nanoparticles have spherical shape with diameter about 13 nm.The transmission electron microscopy and X-ray diffraction patterns are composed of lines that could be indexed within the cubic spinel structure.The room temperature Mössbauer spectrum shows the coexistence of the broad magnetically split part and superparamagnetic doublet.The in-field Mössbauer measurements carried out in the temperature range from room temperature down to 13 K show a gradual increase in the spin canting on the surface of the nanoparticles and decrease in the intensity of the superparamagnetic doublet.The sample was subjected to annealing process performed at elevated temperature in air atmosphere in order to change the microstructure of the nanoparticles and in consequence to change the magnetic properties of the sample.The annealing process leads to the decrease in the value of quadrupole splitting of the superparamagnetic doublets.