Effects of Sm and Mn co-doping on structural, optical and magnetic properties of BiFeO₃ films prepared by a sol-gel technique

Multiferroic (Bi_1-xSm_x)(Fe_0.95Mn_0.05)O₃ (xBSFMO, x=0.00, 0.03, 0.06, and 0.09) films were deposited on the quartz substrates by a sol-gel technique. X-ray diffraction patterns indicate that all the films exhibit a polycrystalline perovskite structure with a high degree of (110) preferred orientation. The Sm and Mn co-doping at A- and B-site of BiFeO₃ (BFO) results in structural distortion, improves surface morphology and reduces the average grain size of the films. With increasing x from 0.00 to 0.09, the optical band gap of xBSFMO films increases and can be expressed by (2.60+0.8x) eV, which may be due to Burstein-Moss effect. Compared with Mn-doped BFO film, the saturation magnetization (M_S) of the (Sm, Mn) co-doped BFO films are significantly enhanced, which provides potential applications in information storage.