Influence of Bi3+ 6s2 lone pair hybridization on the La0.7Pb0.3-xBixMnO3 (x = 0–0.04) crystal structure and electro-magnetic phase transition behaviour

Abstract

Current manuscript focuses on the variations in structural, electrical, and magnetic behaviour exhibited by the new perovskite compound of La0.7Pb0.3-xBixMnO3 (x = 0–0.04). The samples were synthesized using the conventional solid state preparation method. The sample structural properties were determined using X-ray diffraction (XRD), and the diffraction data was refined using Rietveld refinement techniques to determine the samples structural parameters. The XRD analysis shows that the x = 0–0.02 samples crystallized as a single-phase sample, whereas x = 0.04 indicates secondary phase formation of Mn3O4 impurities. Though, all the sample crystallized in a rhombohedral structure with a space group of R-3c. The tolerance factor of the sample was calculated to determine the distortion severity of the structure. Scanning electron microscope (SEM) was used to study the samples' morphological properties. Fourier transform infrared (FTIR) indicates absorption range within 450–600 cm−1 which corresponds with absorption range of Mn–O bond formation. Ultraviolet–visible spectroscopy (UV–Vis) analysis of the sample exhibited an optical energy bandgap within the range of 1.71 eV–2.16 eV. The samples exhibit a clear metal-insulator transition with various TMI values ranging from 256 K until 292 K. Conduction mechanisms at low temperatures (T < TMI) were suggested due to grain or domain boundaries, electron-electron, and electron–magnon mechanisms, while SPH analysis were done to determine the electron conductivity behaviour at high temperatures (T > TMI). The AC susceptibility and Vibrating-sample Magnetometer (VSM) were done to study the magnetic properties of the samples and confirm the transition from ferromagnetic (FM) to paramagnetic (PM) with variation of TC value from 298 K (x = 0) to 289 (x = 0.02) and 287 (x = 0.04).