Influence of Al3+ substituted cobalt nano-ferrite on structural, morphological and magnetic properties

Abstract

The report focuses on studying the structural and magnetic properties of Al3+ substituted cobalt ferrite (CoAlxFe2-xO4, 0.0 ≤ x ≤ 1.0) nanoparticles. The samples have been synthesized by co-precipitation route, followed by annealing at 850 °C during 2 h in air. The X-ray diffraction patterns depict the formation of single cubic spinel structure with Fd-3m space group. Average crystallite size (DX) as well as unit cell parameter (a) were remarkably influenced by increasing Al content. The transmission electron microscopy (TEM) images reveal that grains have an irregular shape and that the mean size of grains decreases with Al content, as seen by XRD experiments with the crystallites behavior. In addition, the energy dispersive X-ray spectrometry analyses show that the samples are chemically homogeneous and the obtained chemical compositions are in agreement with the desired stoichiometry. The scanning electron microscopy exhibits consistence investigations with those observed by TEM. Magnetization-field M(H) curves at 4 and 300 K, highlight that the saturation magnetization and coercivity are considerably influenced by Al content. Thermal variation of the magnetization, M(T), results reveal the existence of inter-particle interactions in the studied samples, further the blocking temperature is found higher than 300 K. Room Mössbauer spectra collected for all samples show a wide effect of Al content on hyperfine properties of Co-ferrite. Indeed, their fits were performed with different components reflecting the incorporation of Fe3+ into A and B sub-structures of ferrite spinel system as the Al content increases. The variation of the hyperfine field, Hhyp, agrees with behavior of Ms as the Al substituent increases from 0.0 to 1.0.