Annealing effect on cobalt-iron oxide: structural and hyperfine investigations

Abstract

The aim of this work is to study the cobalt-iron oxide nanoparticles. This material has been synthesized using flash autocombustion method. The as-prepared sample was calcined at different temperatures such as 450, 650 and 850°C for 2 hours. To investigate the structural, morphological and magnetic properties, the X-ray diffraction technique, scanning electron microscopy and Müssbauer spectrometry were employed. Indeed, X-ray diffraction results reveal that the annealing samples exhibit a cubic spinel structure with space group Fd-Sm- In addition, they do not exhibit any secondary peaks which confirms the formation of single phase, which is cobalt ferrite spinel (i.e. CoFe204). The sample annealed at 850°C shows fine and intense peaks reflecting a good crystallinity of the sample. Otherwise, the scanning electron microscope observations indicate an irregularity of grains shape while the X-ray microanalysis spectra confirm the presence of only Co, Fe and O ions signature of the purity and homogeneity of our samples. On other hand, the 57Fe Mössbauer spectra measured at room temperature present a Zeeman patterns, which are fitted with different components reflecting the ferrimagnetic behavior of the samples. Mössbauer hyperfine parameters were also calculated for each annealed temperature. 850°C is the optimal annealing temperature to obtain spinel ferrite with good crystallinity and hyperfine field of 474.4 kOe.