Magnetic and ferroelectric properties of epitaxial Sr-doped 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 2 P r = 86.13 μ C / cm 2 and coercive field of 2 E C = 75.5 kV / 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 γ - Fe2O3 impurity phase.