Defect formation energy and magnetic properties of aluminum-substituted M-type barium hexaferrite

• DFT results reveal the Al doped barium hexaferrite (BFO) system.
• Saturation magnetization of BFO decreases as Al doping concentration increases.
• Formation energies are compared, and found the site preference for Al atoms.
• Al atoms substitute the majorly contributing magnetic Fe atoms.
• Calculations support the experimental observance of reduced magnetization.

The site occupancy and magnetic properties of aluminum-substituted barium hexaferrite BaAlxFe12−xO19, with the fraction of Al between x = 0.5 and x = 4, has been investigated using density-functional theory within the spin-polarized generalized-gradient approximation. Our results show that Al3+ ions preferentially occupy the 2a and 12k sites, and exclude the occupancy of 4f1 and 4f2 sites (which were not ruled out in previous experimental studies due to the lack of conclusive data). Our results also show that the saturation magnetization decreases monotonically with the increase of Al concentration in agreement with the available experimental data.