Electric field driven destabilization of the insulating state in nominally pure LaMnO3

TL;DR

This study demonstrates that applying an electric field can induce a transition from an insulating to a bad metallic state in LaMnO3, driven by percolation between coexisting phases, with the transition's characteristics strongly dependent on temperature and doping.

Contribution

It reveals a bias-driven percolation transition in LaMnO3 involving coexisting insulating and metallic phases, with detailed analysis of the kinetics and phase behavior.

Findings

Resistive transition occurs below 300 K at a threshold field.

Transition involves a percolation between insulating and bad metallic phases.

The mobile fraction of metallic phase follows activated kinetics with ~200 meV activation energy.

Abstract

We report an electric field driven destabilization of the insulating state in nominally pure LaMnO3 single crystal with a moderate field which leads to a resistive state transition below 300 K. The transition is between the insulating state in LaMnO3 and a high resistance bad metallic state that has a temperature independent resistivity. The transition occurs at a threshold field (Eth) which shows a steep enhancement on cooling. While at lower temperatures the transition is sharp and involves large change in resistance but it softens on heating and eventually absent above 280K. When the Mn4+ content is increased by Sr substitution up to x=0.1, the observed transition though observable in certain temperature range, softens considerably. The observation has been explained as bias driven percolation type transition between two coexisting phases, where the majority phase is a charge and orbitally ordered polaronic insulating phase and the minority phase is a bad metallic phase. The mobile fraction f of the bad metallic phase deduced from the experimental data follows an activated kinetics with the activation energy nearly equal to 200 meV and the prefactor fo is a strong function of the field that leads to a rapid enhancement of f on application of field leading to the resistive state transition. We suggest likely scenarios for such co-existing phases in nominally pure LaMnO3 that can lead to the bias driven percolation type transition.