Influence of Co doping on structural, optical and magnetic properties of BiFeO3 films deposited on quartz substrates by sol–gel method

Multiferroic BiFe1−xCoxO3 (x = 0, 0.03, 0.05, 0.1) thin films have been prepared on quartz substrates using a sol–gel technique. X-ray diffraction data confirms that Co atoms have been successfully incorporated into the host lattice. The scanning electron microscopy (SEM) exhibits that the surface morphologies of BiFe0.97Co0.03O3 and BiFe0.95Co0.05O3 thin films become more compact and uniform. With increasing Co dopant, the position of A1-1 and E-4 modes shift towards the lower wavenumber indicates that Co doping induces structural distortion of BiFeO3. With increasing Co composition, the fundamental absorption edges of BiFe1−xCoxO3 films show red shift. Furthermore, transmittance spectra demonstrates that the optical band gap of BiFe1−xCoxO3 films decreases from 2.66 eV to 2.53 eV with the increase of Co from x = 0 to 0.1. At the wavelength of 720 nm, the refractive index decreases and the extinction coefficient increases with increasing the amount of Co. Optical properties reveal that Co doping in BiFeO3 provides preliminary research for optoelectronic devices and infrared detectors. Compared with BiFeO3 prepared under similar conditions, the remanent magnetization Mr of BiFe1−xCoxO3 (x = 0.03, 0.05, 0.1) thin films significantly enhanced, which provides potential applications in information storage.