Interface-engineered multiferroicity and bandgap tailoring in BFMO/BCO heterostructures

BiFeO 3 -based ferroelectric thin films have attracted much attention for potential applications owing to their advantages of room-temperature multiferroic properties, controllable preparation process, and high remanent polarization. In this work, high-quality BiFe 0.92 Mn 0.08 O 3 /BiCrO 3 composite films were obtained by a sol–gel process and a comprehensive investigation of the film growth, domain structure, multiferroic, and optical properties was provided. These novel BiFe 0.92 Mn 0.08 O 3 /BiCrO 3 films exhibit excellent multiferroic characteristics, which can be used as an absorber layer in ferroelectric photovoltaic solar cells. Moreover, the BiCrO 3 -based interlayers can reduce leakage current density of BiFe 0.92 Mn 0.08 O 3 films, resulting in more efficient ferroelectric properties. The superexchange interaction between Fe and Cr is achieved at the BiFe 0.92 Mn 0.08 O 3 /BiCrO 3 interface by the magnetic coupling between Fe 3＋ and Cr 3＋ ions through paramagnetic oxygen atoms, which enhances the ferromagnetic properties of the films. Amazingly, these polarized materials can be tuned to cover more portion of the solar spectrum as a noteworthy spectral red-shift towards the visible region was discovered. This phenomenon was correlated to an occurrence of ferromagnetism, revealing the significant impact of physical materials non central symmetry structure on their chemical behaviors. These findings demonstrate that the BiFe 0.92 Mn 0.08 O 3 /BiCrO 3 films with a narrow direct band gap possess promising applications in photoelectrochemical and multifunctional devices.