Studies on structural, electrical and optical properties of multiferroic (Ag, Ni and In) codoped Bi0.9Nd0.1FeO3 thin films

Effects of rare earth Nd and (Ag, Ni and In) ions codoping on the structural, electrical, optical, ferroelectric and magnetic properties of the BiFeO3 (BFO) thin films prepared on FTO/glass substrates by using a sol-gel method were investigated. From X-ray diffraction and Raman scattering analyses, distorted rhombohedral perovskite structures were observed for all the films. The X-ray photoelectron spectroscopy analysis was carried out to investigate the chemical states and lattice deficiencies of the films. Both charge states 3+ and 2+ of Fe ions are simultaneously present in all the films but 2+ state appears to be dominant. The leakage mechanisms of the films were systematically investigated by two kinds of bulk-limited conductions (space-charge-limited conduction and Poole-Frenkel emission) and two kinds of interface-limited conductions (Schottky emission and Fowler-Nordheim tunneling). The optical measurement showed that all the films have a conspicuous absorption in the blue and green light region with the band gap values around 2.7 eV. The present work reveals that the non-magnetically active Ag and In ions are more helpful than the magnetically active Ni ion in enhancing the macroscopic magnetization of BFO by the introduction of a local ferromagnetic coupling rather than an antiferromagnetic one.