Comparative study on multiferroic (Bi0.9RE0.1)(Fe0.97Co0.03)O3−δ (RE=Ce and Ho) thin films: Structural, electrical and optical properties

Polycrystalline Bi0.9Ce0.1Fe0.97Co0.03O3−δ and Bi0.9Ho0.1Fe0.97Co0.03O3−δ (BCFC and BHFC) thin films have been deposited on FTO/glass substrates by using a sol–gel method. The influence of Ce, Co and Ho, Co co-doping on the structural, ferroelectric, magnetic and optical properties of the films has been investigated. X-ray diffraction and Raman spectra analyses reveal a lattice distortion for the BCFC film and a structural transition for the BHFC film. The XPS study demonstrates a mixed valence states of the component elements for the BCFC and BHFC films. The Bi-site deficiencies in the BCFC and BHFC films are decreased in comparison to pure BFO film, while the concentrations of Fe2+ ions and oxygen vacancies are increased. The interface-limited Fowler–Nordheim tunneling dominates the leakage currents of the BCFC and BHFC films at the higher applied electric field. The hysteresis loops suggest that the aging effect or domain pinning in the BCFC film is more severe than that in the BHFC film. Highly enhanced magnetization is observed in the BCFC film due to the small grain size effect. The band gap values of the BFO, BCFC and BHFC films estimated from the UV–visible studies are 2.27, 2.57 and 2.59 eV, respectively.