Ferroelectric, magnetic, and optical properties of Aurivillius compound Bi5FeTi2.5Co0.5O15

Bi5FeTi2.5Co0.5O15 (BFTC) ceramics was successfully synthesized using the sol-gel method. It exhibits simultaneously visible-light response, ferroelectric and weak ferromagnetic orders at room temperature. The narrow band gap of 2.06 eV was determined via the UV–vis diffuse absorption spectrum. The x-ray photoelectron spectroscopy results show that the Fe ions in the samples is 3 + and 2 + valence states while the doped Co ions is 2 + valence state. The BFTC sample undergoes a ferromagnetic-like transition at ∼552 K. Weak ferromagnetism is mainly due to spin-canting of Fe-based and Co-based sublattices via Dzyaloshinskii-Moriya (DM) interaction. Dielectric loss and dielectric modulus exhibit the characteristics of dielectric relaxation, which can be ascribed to oxygen˗vacancy hopping. These results reveal many potentially useful physical phenomena and open a new avenue to design of novel solar-energy conversion devices and multiferroic applications.