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The effects of K+ substitution at the Ba-site on the structural, magnetic, and electrical properties and magnetoresistance (MR) of La0.7Ba0.3−xKxMnO3 (x = 0 and 0.04) manganites prepared via the solid-state method were investigated. Rietveld refinement of X-ray diffraction data confirmed that both samples were crystallized in the rhombohedral structure with the R3c¯ space group. In addition, the unit cell volume, V, and the average grain size also increased with K+ ions. Magnetization versus applied field (M–H) measurement was carried out, and the saturation magnetization (Ms) was found to increase from 1.81 μB/f.u. (x = 0) to 4.11 μB /f.u. (x = 0.04), implying that K+ ions strengthened the ferromagnetic (FM) interaction. Furthermore, the metal–insulator transition temperature, TMI, increased from 257 K (x = 0) to 271 K (x = 0.04). The observed behaviour may be related to the enhancement of double-exchange (DE) interaction due to the increase in Mn-O-Mn bond angle and electronic bandwidth (W), favouring the increasing rate of the eg electron hopping process. The fitting of the electrical resistivity data in the metallic region describes the significance of residual resistivity, electron–electron and electron–magnon scattering processes to elucidate the electronic transport properties. Within the insulating region, variable range hopping (VRH) and small polaron hopping (SPH) models are proposed to describe the conduction mechanism.

A new series of Sr2TiCo1−xMnxO6 (0.0 ≤ x ≤ 0.7) materials has been synthesized using the conventional solid-state method. In this research, X-ray diffraction (XRD) results showed that Mn was successfully doped at the Co site in a cubic structure with monoclinic P21/n space group. The effect of Mn cation substitution on the structural, optical and electrical performance of Sr2TiCo1−xMnxO6 double perovskite was investigated. The optical study revealed a nonlinearity pattern of the band gap that is referred to as the band gap bowing trend. Results from optical and Rietveld refinement supports that the band gap bowing trend is correlated with the charge distribution that produces unique effects on structural and size changes due to the Co-Mn compositions. The morphological scanning electron microscopy studies also showed that larger crystallite sizes were developed when dopant was added. Furthermore, increases in the conductivities support the lowering band gap of Mn-doped samples. Here, the intermixing of the atomic orbitals of Co-Mn provides an efficient interlink electrical pathway to improve conductivity and exhibits a high dielectric property at room temperature. These values are strong evidence that STCM material will be suitable for applications in the semiconductor industry.

This study reports the structural, morphological, and magnetic properties of ruthenium doping at the manganese site in Pr0.67Ba0.33MnO3 manganites. Rietveld refinement X-ray powder diffraction (XRD) data show that Pr0.67Ba0.33MnO3 and Pr0.67Ba0.33Mn0.9Ru0.1O3 crystallize in an orthorhombic perovskite structure with the Pnma space group. Doping with Ru yields an increment in the lattice parameter and unit cell volume. In addition, small changes in the Mn–O–Mn bond angle and bond distance are observed. Field emission scanning electron microscopy (FESEM) is used to examine the surface morphology of the samples. Fourier transform infrared spectroscopy (FTIR) reveals that the Mn–O and metal–oxygen bonds appear at the 600 and 900 cm−1 bands, respectively. The AC magnetic susceptibility measurement studies confirm that a paramagnetic (PM) to ferromagnetic (FM) transition exists at 130 and 153 K for the Pr0.67Ba0.33MnO3 and Pr0.67Ba0.33Mn0.9Ru0.1O3 samples, respectively.