Low temperature electrical transport in Ag substituted LaMnO3 polycrystalline pellets prepared by a pyrophoric method

A detailed investigation of the electrical resistivity of a series of monovalent (Ag) doped polycrystalline La1-xAgxMnO3 pellets with x ranging from 0.05 to 0.30 and measured over the temperature range between 10 and 350 K is reported. La1-xAgxMnO3 compounds have been prepared by a novel pyrophoric technique. XRD analysis of our samples indicates single phasic nature for samples with Ag content less than or equal to0.15, while samples with higher Ag content (x greater than or equal to 0.2) show presence of both magnetic perovskite and non-magnetic Ag phases. A sharp insulator-metal transition with T-MI, close to room temperature arising out of the paramagnetic to ferromagnetic transition, and a large magneto-resistance (MR = similar to16%) near T-MI has been observed for all the Ag doped samples. Between T-C(T-pl) and 350 K, all the samples show activated conduction following the Emin-Holstein theory of adiabatic small polaron hopping, while at lower temperatures, in the ferromagnetic regime resistivity appears to be governed by various electron scattering processes. Between 20 and 50 K, a distinct minimum for both H = 0 and H = 0.8 T has been observed, which is explained in terms of inelastic scattering and electron-electron interactions. (C) 2004 Elsevier Ltd. All rights reserved.