The Effect of Zn-Substitution on the Anomalous Resistance Behavior of La1−xCaxMn1−yZnyO3 Compounds

Abstract

We have studied the effect of Zn substitution on the temperature dependence of the resistivity and the Curie temperature T p of La1−xCa x Mn1−yZn y O3 system (with x=0, y=0, and x=0.33, 0.00≤y≤0.15) during their pass to the paramagnetic conducting phase. All the specimens show a clear metal-insulator transition passing through the Curie temperature T p . With increasing Zn concentration, T p decreases for La/Ca substitution and also for Zn/Mn substitution with fixed 33 at.% of Ca. T p is found to be slightly decreases for low concentrations of Zn (up to y=0.075) followed by a sharp decrease up to y=0.15. A possible explanation is given. Moreover, the activation energy Ea is calculated in the three different temperature regions characterized in the (ρ-T) curve. Decreasing the temperature below T p can increase the parallel alignment of the Mn spins and, thus decreases the resistivity of the samples. Ea increases with Zn content (up to y=0.075) followed by a sharp decrease. A strong correlation in the behavior of the normal state and residual resistivity as well as T p and Ea with Zn content is reported.