Effect of Tb-doping on structural, magnetic and optical properties of BiFeO₃ films prepared by chemical solution deposition

Single-phase multiferroic Bi_1-xTb_xFeO₃ (xBTFO, x=0.00, 0.03, 0.06 and 0.09) films were deposited on quartz substrates by chemical solution deposition. X-ray diffraction patterns indicate that all films exhibit a distorted pseudo-tetragonal perovskite structure with a high degree of (110) preferred orientation. The Tb-doping at A-site of BiFeO₃ (BFO) results in lattice contraction, improves surface morphology and reduces the average grain size of the films. One A mode and five E modes of films are observed in Raman scattering spectra, and the position of A mode shifts to higher wavenumber with the increasing of x due to the enhanced Bi-O covalent by Tb doping. With increasing x from 0.00 to 0.09, the saturation magnetization of xBTFO films increases and can be expressed by Ms=(34.6x+1.1) emu/cm^-3, originating from different bond interactions between 4f, 5d orbitals of Tb-O and 6p orbitals of Bi-O. Compared with BFO film, the band gap of xBTFO films decreases, which is mainly due to the increased the tailing of the conduction band edge into the band-gap, which is leading to decreasing the band gap.