Investigation of structural and magnetic properties of Al substituted Ba0.9La0.1Fe12-xAlxO19 hexaferrites prepared by solid-state reaction method

Abstract

The structural and magnetic properties in the Ba0.9La0.1Fe12-xAlxO19 hexaferrite compound were studied as a function of Al3+ concentration (x = 0.0 to 1.3). The samples were obtained by solid-state reaction synthesis and sintered by the conventional ceramic method. The Rietveld refinement method analysis showed the predominance of barium hexaferrite phase with hexagonal structure characterized by P63/mmc space group. The secondary phase of hematite (α-Fe2O3), with rhombohedral system and R-3c space group, was found. For the principal phase, the lattice parameters a, c, and the cell volume (V) reached a minimum value in the concentration x = 0.7 of Al3+ ion. Variations in the average bond length and distortion index of the oxygen polyhedra were observed at the Ba(2d) site and at the Fe (2b, 4fIV, 4fVI, and 12 k) sites. The Raman spectra showed all bands related to FeO bonds at different crystallographic sites. The saturation magnetization reached the minimum value for the composition x = 0.7. The coercive field increased until reaching the maximum value at x = 1.0 of Al3+ concentration. The magneto-crystalline anisotropy field decreased from x = 0.1 to 0.7 and increased at higher concentrations. At room temperatures the total magnetic moment decreases from μ = 10.74 to 4.33 μB for Al3+ concentration range of 0.1 ≤ x ≤ 0.7 and oscillates with μ = 8.18 and 9.44 μB at compositions of x = 1.0 and 1.3, respectively. The present study is important to understand the impact of Al and La addition on the structural and magnetic properties of barium hexaferrite.