Impact of Al³⁺ substitution in M-type hexaferrite on structural, magnetic, and dielectric properties

Abstract Hexaferrites SrAl x Fe 12−x O 19 (x = 0, 1, 2, 3, and 4) doped by Al 3+ in an account of Fe 3+ were synthesized using microwave digestion. X-ray diffraction pattern analysis revealed that the compound is polycrystalline with a hexagonal M-type structure of SrAl x Fe 12−x O 19 and P63/mmc space group is predominant for all dopants of Al 3+ ion. The crystallite size of the SrAl x Fe 12−x O 19 phase has a maximum value for the un-doped sample (94.5 nm) and then decreases for all values of Al-doping. The SEM results showed that the average grain size increased with Al-doping till x = 2 and was almost stable. The magnetic properties were investigated by vibrating sample magnetometer. The results showed a continuous decrease in both saturation (Ms), and remnant (Mr), magnetization with Al-doping. At the same time, the coercive magnetic field, H c , increases continuously with Al-doping except for x = 4, H c slightly decreased. These results make these compound candidates to be used in data storage and magnetic memories. Dielectric properties investigation showed low-frequency dispersion in the dielectric results due to a space-charge effect. It has been demonstrated that enhancements in conductivity, dielectric constant ( ε ′), and dielectric loss ( ε ′′) rise with an increase in the concentration of Al 3+ ions, suggesting that SrAl x Fe 12−x O 19 can be used for microwave absorption and other high-frequency applications.