Effect of molar concentration on structural, magnetic domain and optical properties of BiFeO3 thin films

Abstract

Pure crystalline bismuth ferrite BiFeO3 (BFO) thin films have been deposited on the cleaned glass substrate by sol–gel spin-coating technique with different molar concentrations (from 0.1 to 0.5 M) of the precursor solution. The influence of molar concentrations on the structural, magnetic and optical properties has been investigated by different advanced techniques. The X-ray diffraction patterns of BFO films revealed that the increase of the molar concentration from 0.1 to 0.5 M induced the structural transformation from distorted orthorhombic to single orthorhombic phase. The average crystallite size of BFO thin films was calculated using Scherrer formula and found to be in the range of 15–28 nm. The elemental composition of Bi, Fe and O was confirmed using energy-dispersive spectroscopy of X-rays. The atomic force microscopic images revealed that shape of particles are changing from ellipsoid to nanorods with increasing the molar concentration from 0.3 to 0.5 M. The root means square roughness of BFO films was also varying from 6.34 to 29.88 nm. The stripe-like structure of domain was explored through magnetic force microscopy. The films prepared from the precursor of molar concentration of 0.5 M revealed the microscopic remnant magnetization of 0.19 emu/cm3 and coercivity of 443.06 Oe from the M–H measurements. This enhancement of ferromagnetic properties may be due to the formation of nanorods resulted by destroying the cycloid spin structure. The optical bandgaps were also tuned from 2.58 to 2.49 eV due to increase of the crystallite size from 15 to 28 nm.