Influence of transition elements doping on structural, optical and magnetic properties of BiFeO₃ films fabricated by magnetron sputtering

Bi_0.9La_0.1Fe_1-xCr_xO₃ (x=0.03, 0.05 and 0.07) thin films were deposited on LaNiO₃/Si and quartz by RF magnetron sputtering, respectively. X-ray diffraction patterns indicate that all phases belong to BiFeO₃, and no secondary phase is detected. Three A₁ modes and six E modes of the films are observed in Raman scattering spectra, and the A₁-1 peak position shows red shift with the increasing of x, which indicates that the Cr doping induces more structural distortion. The band gap of the films for x=0.03, 0.05 and 0.07 can be expressed by (2.99-x) eV, which is due to the Cr doping that increases the tailing of conduction band edge into the band gap. With the Cr content increasing from 3% to 7%, the remnant magnetization and the magnetization at 10 kOe of the films show about 202% and 55% addition, respectively.