Low temperature electrical transport in Ag substituted LaMnO 3 polycrystalline pellets prepared by a pyrophoric method

Abstract

A detailed investigation of the electrical resistivity of a series of monovalent (Ag) doped polycrystalline La 1− x Ag x MnO 3 pellets with x ranging from 0.05 to 0.30 and measured over the temperature range between 10 and 350 K is reported. La 1− x Ag x MnO 3 compounds have been prepared by a novel pyrophoric technique. XRD analysis of our samples indicates single phasic nature for samples with Ag content ≤0.15, while samples with higher Ag content ( x≥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=∼16%) near T MI has been observed for all the Ag doped samples. Between T C( T p1) 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.