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 (M-s) and magneton number (n(B)) decrease with increasing Al3+ substitution from 61.2 to 28.9 emu/g and from 12.2 to 5.3 mu(B) 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 approximate to 0.69-0.14 for BaFe12O19. It decreases with increasing temperature, indicating that the heterogeneous structures increase. While the dielectric constant (epsilon') and the dielectric loss (epsilon '') decrease with increasing Al substitution. (C) 2013 Elsevier B.V. All rights reserved.