Structural, optical and magnetic characteristics of multiferroic [Pb(Fe${}_{0.5}$Nb${}_{0.5}$)O${}_3$]${}_{0.4}$ - [(Ca${}_{0.2}$Sr${}_{0.8}$)TiO${}_3$]${}_{0.6}$

We report a detailed and systematic investigation of the multifunctional properties of calcium strontium titanate [(Ca${}_{0.2}$Sr${}_{0.8}$)TiO${}_3$] substituted lead iron niobate [Pb(Fe${}_{0.5}$Nb${}_{0.5}$)O${}_3$] ceramic oxide manufactured by the effective high temperature solid state reaction method. Rietveld studies reveal the single phase formation of the compound with a pseudocubic structure. The Williamson-Hall analysis predicts the presence of tensile strain. The perovskite Ti-O stretching vibrations, Nb-O and C=O vibrations were analyzed by Fourier transform infrared analysis. The O-Ti-O, TiO${}_6$ and Nb-O-Fe stretching vibrations were analyzed using Raman spectroscopy technique. The micro-structural analysis shows formation of dense material. Energy dispersive X-ray spectroscopy analysis describes the purity of the sample. The dual oxidation states of Nb, Ti, Fe and presence of oxygen vacancy were analyzed by incorporating the efficient X-ray photoelectron spectroscopy (XPS) technique. UV-Visible analysis revealed a narrow band gap useful for photocatalytic activity and Urbach energy analysis predicted the crystalline nature of the sample. Effect of structural distortions, oxygen vacancies and electro-negativity on band gap are discussed. The electrical properties were analyzed in the frameworks of dielectric constant, tan δ, complex impedance spectroscopy and conductivity studies. The Jonscher's law analysis shows the presence of correlated barrier hopping (CBH) conduction mechanism. The binding energy (W${}_m$), minimum hopping length (R${}_{min}$) and density of states near Fermi level (N(E${}_F$)) were analyzed. The extracted remnant polarization and coercive field are around to be 0.033 µC/cm${}^2$ and 1.46 kV/cm, respectively, which reveal the presence of weak ferroelectricity. The remnant magnetization and coercive field are around 0.057 emu/g and 0.41 kOe, respectively, indicating the presence of weak ferromagnetism in the sample. The room temperature ${}^{57}$Fe Mössbauer spectroscopy revealed the presence of the high spin Fe${}^{3+}$ species in the octahedral environment with a paramagnetic doublet.