Structure and magnetic properties of the porous Al-substituted barium hexaferrites

Abstract Ion substitution is considered to be one of the efficient approaches to improve the magnetic properties of the barium hexaferrites. In this work, we fabricated BaFe12−xAlxO19 (x = 0, 1, 2, 4, 6) via a simple auto-combustion method and investigated their structures, morphologies and magnetic properties. The coercivity is greatly affected by annealing temperature and Al3+ content. In addition, the Al3+ substitution sites in BaFe12−xAlxO19 were further investigated by the Mossbauer spectroscopy and the superparamagnetic components were found in the BaFe8Al4O19 and BaFe6Al6O19. The highest coercivity of 13.7 kOe was achieved in the BaFe8Al4O19, which increases by 168.6% compared with that of BaFe12O19. This work opens up a new and meaningful insight for the understanding of microstructure and coercivity mechanism towards the Al3+ substituted barium hexaferrites.