Origin of resistivity minima at low temperature in ferromagnetic metallic manganites

TL;DR

This study investigates the low-temperature resistivity minimum in La0.7Ca0.3MnO3 thin films, attributing it to inhomogeneities causing tunneling barriers that affect charge transport.

Contribution

It provides experimental evidence linking resistivity minima to phase inhomogeneities and tunneling effects in ferromagnetic manganite thin films.

Findings

Large hysteresis in magnetoresistance at low temperatures.

Resistivity minima affected by sample current.

Inhomogeneities cause tunneling barriers impacting resistivity.

Abstract

The resistivity and magnetoresistance measurements were carried out on thin film of La0.7Ca0.3MnO3 to investigate the possible origin of low temperature resistivity minimum observed in these samples. We observed large hysteresis in the magnetoresistance at low temperature; 5K and the sample current I has large effect on resistivity minima temperature. The observation of hysteresis at low temperatures suggests the presence of inhomogeneity at low temperatures. These in-homogeneities consist of regions of different resistive phases. It appears that the high resistive phase prevents the tunneling of charge carriers between two low resistive regions and thus giving rise to the resistivity minimum in these samples.