First-principles Study on Electronic and Magnetic Properties of Mn-doped Strontium Ferrite SrFe12O19

To reveal influence of doping ions on the magnetic properties of strontium ferrite materials with magnetoplumbite configurations, we studied the stable configurations and magnetic structures of strontium ferrite with and without manganese doping. The results show that the strontium ferrite is ferrimagnetic, which is consistent with the previous reports. Comparing the GGA and GGA+U approaches, the U value exhibits a significant impact on the electronic structures and atomic magnetic moments. When 3.7 eV is adopted for U value, the system changed from a metal to a semiconductor with a spin up band gap of 1.71 eV. The total magnetic moment of the pure strontium ferrite is 40 mu(B). For the SrFe12-x MnxO19 system, the site preference of Mn substituting Fe is investigated with x=0.5 and x=1.0. When x = 0.5, the single doping Mn atom preferentially occupies the Fe (12k) site. For x=1.0, the two Mn atoms preferentially occupy the Fe (12k) and Fe (2a) sites, respectively. Doping Mn has little impact on the lattice structure of strontium ferrite, but have a significant effect on the total magnetic moments and electronic structures. When x=0.5 and x=1.0, the band gap values for spin up electrons reduced to 0.85 and 0.49 eV, and the total magnetic moments reduced to 39 and 38 mu(B), respectively. This study may provide a theoretical foundation for future experimental studies.