Magnetic and ferroelectric properties of epitaxial Sr-doped BiFeO3 thin films

We investigate the magnetic and ferroelectric properties of epitaxial Sr-doped BiFeO3, i.e., Bi0.75Sr0.25FeO3−δ, thin films prepared by pulsed laser deposition. The films deposited at high oxygen pressure show a ferroelectric hysteresis loop at room temperature with remnant polarization of 2Pr=86.13μC/cm2 and coercive field of 2EC=75.5kV/cm. Compared with the epitaxial BiFeO3 thin film, the remnant polarization and coercive field of Bi0.75Sr0.25FeO3−δ are small, probably due to the dilution of Bi3+ ions, the existence of oxygen vacancies, and a small domain size. On the contrary, the films deposited at low oxygen pressure show a ferromagnetic hysteresis loop at room temperature. However, x-ray absorption and x-ray magnetic circular dichroism measurements show that the observed magnetic moment might be related to the formation of a γγ- Fe2O3 impurity phase.