Study of some co-precipitated manganite perovskite samples-doped iron

Abstract

Polycrystalline La 0.70Sr 0.30Mn 1− y Fe y O 3 (0.05⩽ y⩽0.07) samples are prepared by the co-precipitation method and have been studied. The substitution of Mn 3+ by Fe 3+ reduces the number of available hopping sites for the Mn e g(↑) electron and suppresses the double exchange (DE), resulting in the reduction of the metal–semiconductor transition temperature ( T P) and the flux density saturation ( B s). Low-temperature resistivity ( ρ) data (below T P) well fit with the relation ρ( T)= ρ 0+ ρ 2 T 2, indicating the importance of grain/domain boundary effects and electron–electron scattering processes in the conduction of these materials. On the other hand, at high temperature ( T P< T< θ D/2) conductivity data satisfy the variable range hopping (VRH) model. For T> θ D/2 the small polaron hopping model is more appropriate than the VRH model.