Abstract:
The monophase polycrystalline hexaferrites Ba1−xSrxFe12O19 for 0 ≤ x ≤ 0.75 were prepared using the sol–gel synthesis method. The average crystallite size (Dac) ranged from 47 to 50 nm with Sr doping. The crystal structure and magnetic properties have been studied using X-ray diffraction (XRD) and neutron diffraction (ND). The structure of the studied hexaferrites is described by the hexagonal symmetry of P63/mmc space group. Field-emission scanning electron microscopy (FE-SEM) revealed the heterogeneous distribution of the grain sizes, which takes the hexagonal shape. Energy-dispersive X-ray spectroscopy (EDS) showed that the element compositions agree with the used components for each prepared sample. The substitution of Ba2+ ions by Sr2+ enhances the thermal stability of these hexaferrites. The magnetic hysteresis loops for the studied hexaferrite samples were obtained at room temperature. Different magnetic parameters are given in this work. The magnetocrystalline anisotropy parameter (Keff) initially increases for x ≤ 0.5 and then decreases for (x = 0.75). According to the analysis of neutron data, the magnetic structure formed by the Fe3+ ions, is located in five non-equivalent crystallographic sites with tetrahedral (Fe3-4f1), octahedral (Fe1-2a, Fe4-4f2, and Fe5-12k), and trigonal bipyramidal (Fe2-2b) coordinations. The strontium doping BaFe12O19 (BFO) hexaferrite affects the crystal lattice parameters, bond lengths, bond angles, and ordered magnetic moments of iron. Finally, the enhancement of the thermal stability and some magnetic parameters of the studied hexaferrite samples could be important for applications.
