Effects of non-magnetic Ti⁴⁺ ion substitution at Mn site on structural, magnetic, and optical properties for La_0.57Pr_0.1Sr_0.33Mn_1−xTi_xO₃ manganites

Thermal, morphological, structural, magnetic, and optical properties of manganite samples with La_0.57Pr_0.1Sr_0.33Mn_1−xTi_xO₃ (0 ≤ x ≤ 0.2) compositions were investigated in this work. Thermogravimetric analysis was used to study the percentage weight loss of the compounds during their synthesis by the standard solid-state reaction. Scanning electron microscope (SEM) with an energy dispersive X-ray (EDX) spectrometer shows homogeneous particle distribution and atomic compositions close to the nominal ones. The Rietveld refinement of the X-ray diffractograms revealed that all samples crystallize in the orthorhombic structure with Pnma space group. With Ti substitution, the unit cell volume (V) and average < d_Mn,Ti–O > bond distance increase, whereas the average < θ_{Mn,Ti–O–Mn,Ti} > bond angle and the bandwidth (W) decrease. The Curie temperature (T_C) decreases from 359 K for x = 0 to 320 K for x = 0.2. Likewise, saturation magnetization (M_s) decreases from 44.992 to 15.452 emu/g by increasing Ti content from x = 0 to x = 0.2, respectively. The decrease of both T_C and M_s values was attributed to the structural changes especially to the increase of the bond distance and the decrease of the bandwidth. Additionally, significant lower coercivity values were observed, making the La_0.57Pr_0.1Sr_0.33Mn_1-xTi_xO₃ manganites promising candidates for recording media. The prepared samples exhibited remarkable ultraviolet absorption based on the ultraviolet–visible optical absorbance. Estimated values of band gap energy increase from 4.19 eV for x = 0 to 4.38 eV for x = 0.2 which is attributed to the reduction of the bandwidth (W). The variations with a wavelength of penetration depth and extinction coefficient have been also investigated.