Abstract
Cu2+ ions substituted BaFe12O19, Ba1-xCuxFe12O19 (x ≤ 0.5), nano-sized hexaferrites were fabricated via citrate sol-gel combustion method. X–ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), Energy dispersive X-ray spectroscope (EDXS) and EDS Elemental mapping were used for structural morphological and chemical compositions. These techniques demonstrated the M-type hexagonal structure and the purity of elaborated nanohexaferrites and indicated a reduction of the crystallites size with rising the content of Cu. The impact of Cu-ions substitutions on AC susceptibility measurements of Ba nanohexaferrites were investigated. The magnetic responses of AC susceptibility experiments are depended on external applied frequency. The non-substituted product BaFe12O19 exhibit a value of blocking temperature (TB) around 53 K. TB increased significantly for Ba0.9Cu0.1Fe12O19 nanohexaferrites to be around 158 and afterward reduced to be around 25.5 K for higher amount of Cu elements for Ba0.5Cu0.5Fe12O19 nanohexaferrites. The variation of blocking temperatures of nanoparticles matches very well with the variations of crystallites size. It is found that the TB of nanoparticles increased with reducing the size of nanoparticles and vice versa. Different models have been employed to understand the behavior of AC susceptibility of the magnetic nano-sized particles. The Ea/kB and Keff values are enhanced for Ba0.9Cu0.1Fe12O19 nanohexaferrites compared to non-substituted one, indicating a strengthening of magnetic interactions between nano-sized particles for lower Cu amount. The obtained results suggest that this nano-sized system can be very promising candidate as magnetic recording materials and for many other applications. Besides, it is found that for higher Cu content (Ba0.5Cu0.5Fe12O19 nanohexaferrites) the magnetic interactions are negligible.