Magnetic behavior and dielectric properties of aluminum substituted M-type barium hexaferrite

Various parameters in the structural features of the aluminum substituted barium hexagonal ferrite particles BaAlxFe12−xO19 with 0≤x≤3.5 which were prepared by the solid state reaction method have been studied. The infrared transmission spectrum was measured in the wave number region 5000-200 cm−1 at room temperature. The results were interpreted in terms of the vibrations of the isolated molecular units in such a way to preserve the tetrahedral and octahedral clusters of metal oxides in the barium aluminum hexagonal ferrites. The infrared features are assigned to Fe-O and Ba-O bonds in M-type hexagonal ferrite (BaFe12O19) molecules. Also, the results explain the structural model, based on the effect of aluminum substitution “Al-O bond”. On the other hand, the magnetic behavior of the samples was studied using the vibrating sample magnetometer technique. The saturation magnetization (Ms) and magneton number (nB) decrease with increasing Al3+ substitution from 61.2 to 28.9 emu/g and from 12.2 to 5.3 µB respectively. Also, all samples were characterized using X-ray diffraction and the values of grain size, microstrain and dislocation density of all samples were calculated. The dielectric parameters and ac conductivity measurements were performed within a temperature range 293-493 K. The ac conductivity showed a linear relation with the frequency power law with an exponent s≈0.69-0.14 for BaFe12O19. It decreases with increasing temperature, indicating that the heterogeneous structures increase. While the dielectric constant (ε′) and the dielectric loss (ε″) decrease with increasing Al substitution.