Interacting spin waves in the ferromagnetic Kondo lattice model

TL;DR

This paper introduces a novel method to analyze the ferromagnetic Kondo lattice model, enabling the calculation of magnon energies and lifetimes, and revealing phenomena like anomalous softening and damping at finite temperatures.

Contribution

The authors develop a new approach combining a modified RKKY interaction and spectral density methods to study spin waves in the Kondo lattice model.

Findings

Observation of anomalous softening of magnons

Detection of anomalous damping of spin waves

Effective mapping onto a Heisenberg model

Abstract

We present an new approach for the ferromagnetic, three-dimensional, translational-symmetric Kondo lattice model which allows us to derive both magnon energies and linewidths (lifetimes) and to study the properties of the ferromagnetic phase at finite temperatures. Both "anomalous softening" and "anomalous damping" are obtained and discussed. Our method consists of mapping the Kondo lattice model onto an effective Heisenberg model by means of the "modified RKKY interaction" and the "interpolating self-energy approach". The Heisenberg model is approximatively solved by applying the Dyson-Maleev transformation and using the "spectral density approach" with a broadened magnon spectral density.