High Temperature Thermodynamics of the Ferromagnetic Kondo-Lattice Model

TL;DR

This paper develops a high temperature series expansion for the ferromagnetic Kondo lattice model to analyze magnetic and charge properties relevant to CMR perovskites, highlighting the limitations of static models for explaining the CMR effect.

Contribution

It introduces a high temperature series expansion for the ferromagnetic Kondo lattice model in the large coupling limit, providing insights into magnetic transition temperatures and charge excitations.

Findings

Cross-over to Curie-Weiss behavior at a temperature related to bandwidth

Estimated magnetic transition temperatures match experimental data

Charge excitations can be modeled by spinless fermions at high temperatures

Abstract

We present a high temperature series expansion for the ferromagnetic Kondo lattice model in the large coupling limit, which is used to model CMR perovskites. Our results show the expected cross-over to Curie-Wei{\ss} behavior at a temperature related to the bandwidth. Estimates for the magnetic transition temperatures are in the experimentally observed range. The compressibility shows that the high temperature charge excitations can be modeled by spinless fermions. The CMR effect itself, however, warrants the inclusion of dynamic effects and cannot be explained by a static calculation.