Cr doping-induced structural phase transition, optical tuning and magnetic enhancement in BiFeO3 thin films

BiFe1−xCrxO3 (xBFCO, x=0, 0.03, 0.06 and 0.09) polycrystalline films have been prepared on quartz substrates by a sol-gel technique. X-ray diffraction clearly reveals the crystal structure of xBFCO thin films transforms from rhombohedral to orthorhombic, moreover, inter planar spacing and grain size of xBFCO are reduced slightly. Scanning electron microscopy shows that Cr doping can improve surface morphology and reduces the average grain size of the films. The photoluminescence (PL) spectra of xBFCO thin films at room temperature show a strong emission in the blue region. With increasing x from 0.00 to 0.09, the band gap (Eg) of xBFCO films decreases and can be expressed by Eg=(2.58−0.67x) eV. Compared with BiFeO3 film, the saturation magnetization of xBFCO (x=0.03, 0.06 and 0.09) films is significantly enhanced, which provides potential applications in information storage.