Study of magnetization and transport properties in La 0.7Pb 0.3MnO 3 with the addition of nonmagnetic Ag

Abstract

Magnetization and transport properties of Ag containing La 0.7Pb 0.3MnO 3+ x wt% Ag ( x=0–20) system have been reported. The samples with high Ag content ( x>10), Ag phase is observed along with the perovskite structure. Presence of non-magnetic Ag in La 0.7Pb 0.3MnO 3 decreases the d.c magnetization along with increase of ferromagnetic Curie temperature. All the samples show metal-insulator transition (MIT) with peaks at the MIT temperatures (T p ∼240–340 K depending on Ag content). Resistivity ( ρ) decreases and T p increase with increase of Ag content. For higher concentration of Ag (>10 wt%) decrease of ρ is small and T p remains almost constant. Magnetoresistance ratio [MRR=−( ρ 1.5T− ρ 0 T )/ ρ 0 T )] also decreases with increasing Ag concentration. In the semiconducting regime (above T p), resistivity data can be well fitted with small polaron hopping (SPH) model. Activation energy calculated from the SPH model decreases with Ag content. In the low temperature phase ( T< T p), T 2 dependency of resistivity is observed prominent than T 2.5 dependency for the samples with Ag ≥5 wt%, indicating the appearance of strong electron-electron interaction in La 0.7Pb 0.3MnO 3+ x Ag system. Present study indicates the importance of both electron-electron and electron–magnon interactions for explaining transport properties in low temperature phase ( T< T p) of the present La-Pb-Mn-O+Ag system.