Detecting percolative metal-insulator transition in manganites by resistive relaxation

TL;DR

This study investigates the resistive relaxation behavior in ultrathin manganite films to understand the phase separation and percolation mechanisms behind the metal-insulator transition and colossal magnetoresistance.

Contribution

It provides experimental evidence linking resistive relaxation sign changes to phase separation and percolation in manganites during the transition.

Findings

Resistive relaxation rate changes sign at the transition.

Metallic state shows increasing resistivity over time.

Insulating state shows decreasing resistivity over time.

Abstract

We report an experimental study of the time dependence of resistivity of a La$_{0.9}$Sr$_{0.1}$MnO$_{3}$ ultrathin film in order to elucidate the underlying mechanism for metal-insulator transition and colossal magnetoresistance CMR effect. There is a clear change of sign in the resistive relaxation rate across the metal-insulator transition driven by temperature or magnetic field. When measuring in increasing temperature or decreasing magnetic field, the resistivity increases with time in the metallic state but decreases with time in the insulating state. These relaxation processes indicate that the metal-insulator transition and the associated CMR are a direct result of phase separation and of percolation of the metallic phase.