Electrical Transport and magnetoresistance properties of La_0.8Ca_0.2-xAg_xMnO₃ (x = 0 and 0.05)

A systematic investigation of electrical transport and magnetoresistance properties of polycrystalline La_0.8Ca_0.2-xAg_xMnO₃ (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.