Ba and Ti co-doped BiFeO₃ thin films via a modified chemical route with synchronous improvement in ferroelectric and magnetic behaviors

A modified chemical route via the layer-by-layer alternative deposition of BaTiO₃ and BiFeO₃ two compositions followed by the solution processing has been developed to prepare Ba and Ti co-doped multiferroic BiFeO₃ thin films. The Ba and Ti co-doped BiFeO ₃ films crystallize in single perovskite phase and are composed of uniformly distributed grains of tens of nanometers as evidenced by X-ray diffraction and scanning electron microscopy images, respectively. But the films show local composition fluctuation with further high-resolution transmission electron microscope analysis, which leads to increased inner strain and thus a phase transition from R3c to P4mm occurs as Ba and Ti contents reach 50 mol. . Accompanying the structural phase transition, a saturated P-E hysteresis loop with P_r ∼ 27 μC/cm² and P_s ∼ 87 μC/cm² and, moreover, a transition from antiferromagnetic to ferromagnetic state with M_r ∼ 1.46 emu/cm³ and H _c ∼ 1000 Oe have been observed. A strain induced structural change is proposed to explain for the observed synchronous enhancement in ferroelectric and magnetic properties, and elastic energy calculation is carried out to verify the viewpoint on magnetic behavior. The modified multiferroic behaviors of Ba, Ti co-doped BiFeO₃ film imply an improved magnetoelectric coupling, which makes the material good candidate as memory devices and sensors.