Study on Mn-induced Jahn–Teller distortion in BiFeO3 thin films

Abstract

Present work reports Raman spectroscopy study of single-phase Mn-doped BiFeO3 [BiFe1−x Mn x O3 (0 ≤ x ≤ 0.20)] polycrystalline thin films carried out in backscattering geometry. De-convolution of Raman spectra showed a gradual transition in the crystal symmetry from rhombohedral (−R) to multiphase [rhombohedral (−R) + tetragonal (−T)] structure with increasing Mn doping concentration in BiFe1−x Mn x O3 (BFMO) thin films. X-ray diffraction (XRD) along with Le-Bail extraction refinement confirms that the structural symmetry lowering in BFMO thin films occurs at about 10 % Mn doping concentration. A blue shift is observed in the direct energy band gap of BFMO thin films from 2.53 to 2.87 eV (at T = 295 K) and is attributed to the local symmetry lowering and local induced strain in Fe3+ environment resulted from Jahn–Teller distortion in (MnFe)3+O6 octahedral unit. Second-derivative analysis of FTIR spectra in the spectral regions (420–470) cm−1 and (480–680) cm−1 further indicates the favourable structure distortion leading to the simultaneous exhibition of enhanced ferromagnetic and ferroelectric properties owing to Mn substitution in host BiFeO3 lattice.