Comparative study on structural, morphological, and optical properties of MS/Fe3O4 nanocomposites and M-doped Fe3O4 nanopowders (M = Mn, Zn)

In the present work, the un-doped, M-doped magnetite (Fe₃O₄); (M = Mn, Zn), and MS/Fe₃O₄ composite nanopowders with a cubic spinel-type structure and average crystallite size range from 8.30 to 12.33 nm were synthesized by co-precipitation method. The FESEM images revealed the shape of particles are spherical with a grain size in the range of 33.44-49.77 nm. Through the analysis of reflectance data using Tauc's model, the direct band gap energies of 2.98 eV, 2.93 eV, 3.01 eV, 2.85 eV, and 2.95 eV were determined for Un-doped Fe₃O₄, Mn-doped Fe₃O₄, Zn-doped Fe₃O₄, MnS/Fe₃O₄ composite, and ZnS/Fe₃O₄ composite NPs respectively. The parameters such as extinction coefficient and refractive index of the nanoparticles were computed by the Kramers-Kronig (K-K) method. Non-linear optical (NLO) parameters were computed from DRS data using the Wemple-Di-Domenico (WDD) model. The calculated third-order NLO susceptibility <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup><mml:mrow><mml:mi>χ</mml:mi></mml:mrow> <mml:mrow><mml:mo>(</mml:mo> <mml:mn>3</mml:mn> <mml:mo>)</mml:mo></mml:mrow> </mml:msup> </mml:math> and also electrical susceptibility <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>χ</mml:mi> <mml:mfenced><mml:mi>e</mml:mi></mml:mfenced> </mml:msub> </mml:math> represented the maximum value for MnS/Fe₃O₄ composite NPs compared to the other samples. Considering the advanced optical parameters of MS/Fe₃O₄ composite samples, these particles can be suitable candidates for non-linear optical applications.