Low Temperature Magnetic Properties of the Double Exchange Model

TL;DR

This paper investigates the low temperature magnetic properties of the double exchange model, revealing that its ground state is generally not ferromagnetic and its excitations differ from traditional spin waves, indicating unusual magnetic behavior.

Contribution

It provides new insights into the ground state and excitation spectrum of the double exchange model, challenging previous assumptions of ferromagnetic order.

Findings

Ground state is not globally ferromagnetic in general.

Low energy excitations differ from Heisenberg ferromagnets.

Unusual dynamic magnetic properties are predicted.

Abstract

We study the {\it ferromagnetic} (FM) Kondo lattice model in the strong coupling limit (double exchange (DE) model). The DE mechanism proposed by Zener to explain ferromagnetism has unexpected properties when there is more than one itinerant electron. We find that, in general, the many-body ground state of the DE model is {\it not} globally FM ordered (except for special filled-shell cases). Also, the low energy excitations of this model are distinct from spin wave excitations in usual Heisenberg ferromagnets, which will result in unusual dynamic magnetic properties.