Effects of intrinsic defects and doping on SrFe12O19: A first-principles exploration of the structural, electronic and magnetic properties

Effects of intrinsic defects and doping on the M−type strontium hexagonal ferrites (SrFe12O19) has been systematically studied using density functional theory combined with the generalized gradient approximation (GGA) + U method. The energies of possible intrinsic point defects and doping in SrFe12O19 have been determined, and effects of those on the electronic and magnetic properties have been analyzed. The results show that, under an oxygen poor condition, the defects of iron vacancy are difficult to form, while the defects of oxygen vacancy are easy to form. In the case of oxygen rich condition, the defects of iron vacancy are difficult to form when Fermi energy level is close to VBM, however, when Fermi energy level approaches CBM, the defects of iron vacancy in some sublattice sites are tend to form, especially in the 2a sublattice. Meanwhile, under the oxygen rich condition, the defect formation energy of Co substituting for Fe is very low, which indicates that Fe is easy to be substituted by Co, preferentially in 4f2 sublattice, followed by 2a sublattice. The lattice constant of La-Co co-doped is smaller than that of perfect SrFe12O19, meanwhile, the total magnetic moment changes little. The density of states shows that La-Co co-doped SrFe12O19 exhibits n-type semiconductor characteristics.