Enhanced magnetic properties of single domain Al-substituted strontium hexaferrite (SrFe12−xAlxO19) synthesized via hydrothermal method for permanent magnets

Al-substituted strontium hexaferrite (SrFe12–xAlxO19; x ≤ 2.0) materials were synthesized using the hydrothermal technique. The influence of the Al3+ substitution has been examined using the powder X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscope (FE-SEM), and the vibrating sample magnetometry (VSM). Hexagonal phase formation with P63/mmc symmetry for all the compositions was confirmed by XRD study. With the increase of Al3+ concentration, lattice parameters get contracted. Enhanced magnetic properties were observed in the Al-substituted strontium hexaferrite. The morphology of the undoped and doped samples was changes from irregular hexagonal flakes to plate-like (rod-like) shapes. In this study, the energy product (BH)max = 2.05 MGOe and squareness ratio (Mr/Ms) = 0.55 were obtained for an Al concentration of x = 1.5. The maximum value of the anisotropy constant (Keff) was 13.49×106ergcm-3, for Al3+ doping content (x) = 1.5, which is tremendously high and possesses potential for its application as permanent magnets.