Tuning magnetic properties of BiFeO3 thin films by controlling Mn doping concentration

Mn-doped BiFeO3 (BiFe1-xMnxO3, x = 0, 0.03, 0.05, 0.10, 0.15 and 0.20) polycrystalline multiferroic thin films were successfully synthesized using the facile sol-gel spin-coating method. The crystal structures, surface features, elements valences, and magnetic properties of as-prepared samples were systematically explored. X-ray diffraction and Raman spectroscopy studies revealed the substitutions of Mn into the Fe site and a rhombohedral-to-orthorhombic phase transition. The Field Emission Scanning Electron Microscopy showed a decrease in the average particle sizes and an improvement of surface morphology with increasing the concentration of the substitutes. Energy-dispersive X-ray spectroscopy confirmed the doping concentration of Mn2+ in the samples. X-ray photoelectron spectroscopy indicated the co-existence of Mn2+/Mn3+ ions in the doped films. The remnant magnetization value of BiFe0.90Mn0.10O3 thin film was found to be approximately six times than that of pure BiFeO3 thin film under a magnetic field of 10 kOe. The enhanced magnetic property of BiFe0.90Mn0.10O3 thin film was mainly ascribed to the structural distortion of spin cycloid and the enhancement of super-exchange interaction between the Fe3+ (Mn2+) and O2- ions.