Structural transition and tunable optical, morphological and magnetic properties of Mn-doped BiFeO3 films

The effects of Mn-doping on the structural, optical and magnetic properties of BiFe1-xMnxO3 (x = 0.0, 0.02, 0.05) thin films prepared by spray pyrolysis technique have been investigated. X-ray diffraction patterns of the annealed films show the distorted rhombohedral crystal structure with R-3 m symmetry. The average crystallite size of films was calculated and found to decrease from 36 nm to 18 nm with increasing Mn-doping from x = 0 to x = 0.05. The microstructural strains calculated from Williamson-Hall plots, increases from 0.0134 to 0.07576 with increasing the Mn-doping. FE-SEM images show that the surface has fibre like network for x = 0.05 and EDS confirms the presence of Bi, Fe, Mn and O element in appropriate stoichiometry. The periodic strips like magnetic domain structures were explored by magnetic force microscopy. The large value of the remanent magnetisation (0.125 emu/cm(3)) and coercivity (208.35 Oe) of the Mndoped ferrite films from the magnetic (M-H) measurements reveals the enhancement of ferromagnetism via the release of the latent magnetization, locked in the cycloidal spiral structure. The optical band gap and refractive index (n(r)) of films are tuned from 3.386 eV to 3.479 eV and 2.30 to 2.52 respectively with increase of Mn-doping concentrations.