Substitution driven structural and magnetic properties and evidence of spin phonon coupling in Sr-doped BiFeO3 nanoparticles

The manifestation of dimensionalities and Sr induced modifications in structural, vibrational and magnetic properties of Bi1-xSrxFeO3; (x = 0-0.25) nanoparticles synthesized by a tartaric acid based sol-gel route are reported. X-ray diffraction and electron microscopy studies reveal the phase purity and nanocrystalline nature (45-90 nm) of Bi1-xSrxFeO3 samples. The Sr ions substitution motivated the coexistance of rhombohedral (R3c) and pseudo tetragonal (P4/mmm) structural symmetry for the x = 0.25 sample which leads to enhancement of saturation magnetization due to the distorted cycloid spin structure and uncompensated surface spins, which is in concomitance with the electron paramagnetic resonance (EPR) and Mossbauer studies. The ferromagnetic ordering contribution continuously increases with increasing Sr content from x = 0-0.25 samples with a maximum saturation magnetization of 0.72 emu g(-1) for the x = 0.25 sample which is also endorsed by second order Raman modes. X-ray photoelectron and Mossbauer measurements confirmed the dominance of the Fe3+ oxidation state. Alteration in QS hyperfine parameters and line-width analysis have been probed by Mossbauer analysis with increasing Sr content in BiFeO3 nanoparticles suggesting the destruction of the spin cycloid