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

► BiFe1−xCoxO3 (x = 0, 0.03, 0.05, 0.1) thin films were firstly deposited on quartz substrates by sol-gel method. ► The optical band gap of BiFe1−xCoxO3 decreases from 2.66 eV to 2.53 eV with the increase of Co from x = 0 to 0.1. ► Co doping in BiFeO3 provides preliminary research for optoelectronic devices and infrared detectors. ► Compared with BiFeO3, the remanent magnetization Mr of BiFe1−xCoxO3 thin films significantly enhanced.