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In this work, we have investigated the effect of silver substitution on electrical transport behavior and magnetoresistance of La0.8- xAgxCa0.2MnO3 (x = 0 and 0.05). Preparation and study of structural and microstructure of both samples have been reported on previous work. Temperature-dependent resistivity has been measured at temperature range of 15-285 K with zero field cooling. Magnetoresistance effect has been measured at 15, 100, and 285 K with magnetic field up to 1 T. The electrical transport behavior of both samples are quite well described by a theory based on the Percolation model. The electrical conduction mechanism at low temperature can be explained by a theory based on Kondo-like spin-dependent scattering, electron-electron, electron–magnon, and electron-phonon scattering. It was found that silver substitution increases the metal-insulator transition temperature (TM-I) from 197.55 to 277.56 K, and Curie temperature (Tc Mod) from 217.25 to 278.65 K. Moreover, the maximum magnetoresistance value of both samples was obtained at 15 K.

The structure, morphology, electrical transport and magnetoresistance properties of La0.7Ba0.1Sr0.2Mn0.9Cu0.1O3 has been investigated. The sample has been successfully prepared using sol-gel method. Structural investigation using X-ray diffraction (XRD) shows that the sample crystallizes in rhombohedral structure with R3c space group. The surface morphology of the sample shows that the sample consists of irregular polygonal grain. Furthermore, resistivity measurement shows that the sample undergoes a transition from metal to semiconductor behaviour upon heating. The electrical properties of the sample follow the electron-phonon-magnon scattering theory. Under the influence of the external magnetic field, the sample shows that up to 8% of the resistivity decreased at 200 K.

A systematic investigation of electrical transport and magnetoresistance properties of polycrystalline La0.8Ca0.2-xAgxMnO3 (x = 0 and 0.05) is reported in this work. According to the resistivity data measured from 40 to 250 K, transition from metallic to insulator behavior upon heating were observed in both samples. Additionally, 5% silver substitution shifts the metal-semiconductor transition into a higher temperature. Furthermore, silver substitution also decreases the overall temperature compared to the original compound. In this work, this result can be well described using electron-electron, electron-phonon, and the interaction between electron, phonon, and magnon. Resistivity measurements under magnetic field influence shows that silver substitution improves the magnetoresistance properties compared to the original compound. The maximum ratio of magnetoresistance at 285 K was found to be 3.3% and 4.7% for x = 0 and 0.05, respectively.