Effective Mass Ratio & positive colossal magnetoresistance of a Nano-wire

TL;DR

This study investigates the relationship between polarization, effective mass ratio, and magnetoresistance in a one-dimensional nano-wire system using a Hubbard model, revealing how these properties change with temperature and magnetization.

Contribution

It introduces a theoretical relation between polarization, EMR, and MR in 1D systems considering off-diagonal Coulomb interactions, supported by comparison with experimental data.

Findings

EMR decreases with increasing magnetization below transition temperature

MR decreases as the system is cooled below transition temperature

Band narrowing dominates over band splitting due to off-diagonal Coulomb elements

Abstract

In the present work, a relation has been established between degree of polarization and effective mass ratio (EMR) and magnetoresistance (MR) of one-dimensional non-degenerate system (which can represent a nano-wire or a linear chain of atoms and molecules in one dimension) by using a non-degenerate Hubbard model, which includes diagonal and off-diagonal matrix elements of Coulomb interaction. EMR is one of the most important property, which provides information that how much itinerant the system is? Within the mean field approximation, it is found that, due to the presence of off-diagonal elements, the band narrowing effect dominates over the band splitting effect. The EMR varies with degree of polarization. EMR for majority (up spin) carriers decreases as magnetization increases below ferromagnetic transition temperature. MR decreases as system is cooled below the ferromagnetic transition temperature. A comparison of our results with existing experimental observations is made.