Structural, optical and magnetic studies of (Y, Co) co-substituted BiFeO3 thin films

Polycrystalline BiFeO3 (BFO) and Bi0.9Y0.1Fe1-xCoxO3 (x = 0, 0.03, 0.05, and 0.10) thin films were prepared on quartz and Pt(111)/Ti/SiO2/Si(100) substrates using a sol-gel method. X-ray diffraction and micro-Raman measurements demonstrated that the phase of all films was a perovskite-type rhombohedral structure. Bi0.9Y0.1Fe1-xCoxO3 thin films exhibited a merging of (104) and (110) peaks, which indicated obvious distorted deformation of FeO6 octahedra. UV-visible absorption spectra confirmed that the substitutions of Y and Co ions in Bi and Fe sites caused an increase in the optical band gap of BFO thin film, suggesting their potential application as UV and blue-green-driven photocatalysts. The magnetic test indicated that the ferromagnetic behavior was enhanced with the increase of Co ion concentration for (Y, Co) co-substituted BFO films, which could be attributed to the different magnetic moments of Co3+ and Fe3+. The saturation magnetization at room temperature for x = 0.10 sample was 132 memu/cm3. The results revealed that the (Y, Co) co-substitution played an important role for the improved ferromagnetic properties of BFO thin films. The mechanisms of (Y, Co) co-substitution effects on structural, optical and magnetic characteristics of BFO films were discussed.