Double Exchange Model for Magnetic Hexaborides

TL;DR

This paper develops a microscopic double-exchange model to explain the magnetic and transport properties of rare-earth ferromagnetic hexaborides, accurately matching experimental data and predicting Curie temperature behavior.

Contribution

It introduces a detailed double-exchange Hamiltonian tailored for magnetic hexaborides, linking electronic structure with magnetic and transport phenomena.

Findings

Transport properties match experimental measurements

Model predicts Curie temperature dependence on plasma frequency

Quantitative description of Hall effect and magnetoresistance

Abstract

A microscopic theory for rare-earth ferromagnetic hexaborides, such as Eu(1-x)Ca(x)B6, is proposed on the basis of the double-exchange Hamiltonian. In these systems, the reduced carrier concentrations place the Fermi level near the mobility edge, introduced in the spectral density by the disordered spin background. We show that the transport properties such as Hall effect, magnetoresitance, frequency dependent conductivity, and DC resistivity can be quantitatively described within the model. We also make specific predictions for the behavior of the Curie temperature, Tc, as a function of the plasma frequency, omega_p.