Electronic and Magnetic States in the Giant Magneto-resistive Compounds

TL;DR

This paper models the transition from insulator to metal in Lanthanum manganites, linking magnetic and electronic properties, and predicts how magnetic fields influence conductivity and localization.

Contribution

It introduces a theoretical framework considering localization, spin fluctuations, and electron interactions to explain magnetoresistive phenomena in giant magnetoresistive compounds.

Findings

Derived transition temperature and its dependence on composition

Predicted magnetic field effects on localization length and conductivity

Provided testable expressions connecting magnetic susceptibility and transport properties

Abstract

The paramagnetic insulator to ferromagnetic metal transition in Lanthanum manganites and the associated magnetoresistive phenomena is treated by considering the localization due to random hopping induced by slowly fluctuating spin configurations and electron-electron interactions. The transition temperature and its variation with composition is derived. The primary effect of the magnetic field on transport is to alter the localization length, an effect which is enhanced as the magnetic susceptibility increases. Expressions for the conductivity, its variation with magnetic field, and its connection with magnetic susceptibility in the paramagnetic phase are given and can be tested with further experiments.