Spin-wave Hamiltonian in double-exchange systems

TL;DR

This paper derives an effective spin-wave Hamiltonian for double-exchange systems with large Hund's-rule coupling, showing that magnon spectra can be approximated by the Heisenberg model within a certain expansion.

Contribution

It provides a simple derivation applicable to models with arbitrary hopping range and randomness, extending the understanding of spin-wave behavior in double-exchange systems.

Findings

Magnon spectrum described by Heisenberg model

Formalism applicable to models with arbitrary hopping and randomness

Valid within leading order of 1/S expansion

Abstract

A simple derivation of the effective spin-wave Hamiltonian for a double-exchange system with infinitely large Hund's-rule coupling is demonstrated. The formalism can be applied to models with arbitrary range of hopping as well as those with randomness. The result shows that, within the leading order of the 1/S expansion, one magnon excitation spectrum can be described by the Heisenberg model.