Electrical transport and percolation in magnetoresistive manganite / insulating oxide composites: case of La0.7Ca0.3MnO3 / Mn3O4

TL;DR

This study investigates the electrical resistivity and percolation behavior in La0.7Ca0.3MnO3 / Mn3O4 composites, identifying a critical threshold and analyzing how conduction mechanisms change with temperature and composition.

Contribution

It provides experimental evidence of the percolation threshold and critical exponents in magnetoresistive oxide composites, with temperature-dependent analysis of conduction behavior.

Findings

Percolation threshold at ~0.19 La0.7Ca0.3MnO3 volume fraction

Critical exponent t is 2.0 at room temperature

Critical exponent t increases to 2.6 at 5 K due to grain boundary effects

Abstract

We report the results of electrical resistivity measurements carried out on well-sintered La0.7Ca0.3MnO3 / Mn3O4 composite samples with almost constant composition of the magnetoresistive manganite phase (La0.7Ca0.3MnO3). A percolation threshold (fc) occurs when the La0.7Ca0.3MnO3 volume fraction is ~ 0.19. The dependence of the electrical resistivity as a function of La0.7Ca0.3MnO3 volume fraction (fLCMO) can be described by percolation-like phenomenological equations. Fitting the conducting regime (fLCMO > fc) by the percolation power law returns a critical exponent t value of 2.0 +/- 0.2 at room temperature and 2.6 +/-0.2 at 5 K. The increase of t is ascribed to the influence of the grain boundaries on the electrical conduction process at low temperature.