The level shifting induced negative magnetoresistance in the nearest-neighbor hopping conduction

TL;DR

This paper introduces a new mechanism for negative magnetoresistance in granular materials driven by level shifting effects during nearest-neighbor hopping, with temperature and separation dependence.

Contribution

It presents a novel explanation for negative magnetoresistance in non-magnetic granular systems based on level shifting during electron hopping.

Findings

Negative magnetoresistance observed at low temperatures for small cluster separation.

Magnetoresistance changes from negative to positive with increasing temperature or cluster separation.

Magnetoresistance change can exceed 80% at low temperatures.

Abstract

We propose a new mechanism of negative magnetoresistance in non-magnetic granular materials in which electron transport is dominated by hopping between two nearest-neighbor clusters. We study the dependence of magnetoresistance on temperature and separation between neighboring clusters. At a small separation we find a negative magnetoresistance at low temperatures and it changes over to a positive value as temperature increases. For a fixed temperature, magnetoresistance changes from negative to positive when the cluster separation increases. The change of magnetoresistance $\Delta R/R$ can be more than 80% at low temperatures.