Effects of Fe, Co, or Ni substitution for Mn on La0.7Sr0.3MnO3 perovskite: Structural, morphological, and optical analyses

In this work, lanthanum strontium-based perovskites La0.7Sr0.3BO3 (B = Mn, Fe, Co, or Ni) samples are suc-cessfully synthesized. Hexagonal and Rhombohedral phases in the LSMO sample are observed using the XRD results. From reflectance data, the band gap energies are found to be 2.95 eV, 3.19 eV, 3.03 eV, and 3.14 eV for LSMO, LSFO, LSCO, and LSNO, respectively leading to a blue shift after the replacement. Linear optical evalu-ations exhibit increased band gap energy and decreased Urbach energy with the replacement of the Fe, Co, or Ni at the Mn site indicating presence of the localized defect states. The calculated extinction coefficient and refractive index parameters, using the Kramers-Kronig method, represent maximum values at the same wave-length for the LSFO. The nonlinear optical parameters are calculated using the obtained data from Diffuse reflectance spectroscopy. The connection of nonlinear optical absorption (beta) with localized defect states has been discussed.