Dependence of magnetic properties on the Fe ²⁺ ion in Ba-doped BiFeO ₃ multiferroic films

Ba-doped BiFeO ₃ thin films were prepared on Pt/TiO ₂/SiO ₂/Si (100) substrate at various oxygen pressures by pulsed laser deposition. The influences of oxygen pressure on the crystalline structures, magnetic and electrical properties of these films were studied. Studies showed that the oxygen vacancy content and accordingly the leakage current density of the films decreased with the increase of the oxygen pressure, and the concentration of the Fe ²⁺ increased with the decrease of the oxygen pressure. Strong ferromagnetism was observed in these films. The magnetization of the films increased with the decrease of the oxygen pressure and the largest remnant magnetization of 2.46 × 10 ⁴ A/m was obtained at an oxygen pressure of 0.7 Pa. This enhancement of the magnetization can be attributed to the increase of the Fe ²⁺ concentration which may be related closely to the increase of the oxygen vacancy in the films.