Magnetic field dependent variable range hopping behaviour in resistivity at low temperatures in polycrystalline colossal magnetoresistive manganites: evidence of spin polarised tunnelling

TL;DR

This paper reveals variable range hopping behavior in resistivity at low temperatures in polycrystalline CMR manganites, which diminishes under magnetic fields, providing insights into spin-polarized tunneling effects at grain boundaries.

Contribution

It demonstrates the presence of variable range hopping in polycrystalline CMR manganites and its suppression by magnetic fields, offering new understanding of low-temperature magnetoresistance mechanisms.

Findings

Variable range hopping observed at low temperatures.

Magnetoresistance behavior suppressed by magnetic field.

Implications for spin polarized tunnelling at grain boundaries.

Abstract

It has been observed that the low temperature magnetoresistance behaviour in polycrystalline colossal magnetoresistive (CMR) manganites differ significantly from the single crystals. The polycrystalline samples show large magnetoresistance at temperatures much below the ferromagnetic transition temperature where the magnetoresistance of single crystals is very small. This has conventionally been attributed to spin polarised tunnelling at the grain boundaries in polycrystalline samples. In this paper we show the existence of a variable range hopping behaviour in resistivity at low temperatures in polycrystalline CMR samples. This behaviour gets gradually suppressed under the application of magnetic field. We discuss the significance of these results with respect to spin polarised tunnelling.