Investigations on electrical, magnetic and optical behaviors of five-layered Aurivillius Bi₆Ti₃Fe₂O ₁₈ polycrystalline films

Five-layered Aurivillius Bi₆Ti₃Fe₂O ₁₈ (BTF2) polycrystalline thin films were prepared by a chemical solution deposition route. The crystalline structures and microstructures were characterized by X-ray diffractometer, micro-Raman spectrometer and atomic force microscopy. Its electrical and magnetic properties were investigated, and especially optical properties were addressed in detail. Coexistence of the ferroelectric and weak ferromagnetic properties indicated the multiferroic behavior of the BTF2 films. The optical dielectric functions in the photon energy range of 1.13-4.13 eV have been extracted by fitting the experimental data in the light of the Tauc-Lorentz dispersion model. A direct interband transition with bandgap energy ∼ 3.72 eV was determined for the BTF2 films. The weak absorption below band-gap edge was explained by the Urbach band tail rule. Finally, the optical dispersion behaviors of the BTF2 films in the transparent oscillating region were described using a single oscillator model.