Magnon excitation and nonlinear dynamics

Abstract

This chapter is devoted to the study of linear and nonlinear processes and techniques for the excitation of magnons. In the presentation of the linear excitation process we employ three different quantum approaches that are commonly used and show that they are all consistent. The last one serves to show that the magnons excited by microwave radiation are in quantum coherent states. The theory is used to interpret experimental measurements. A quantum approach is also used to study the parametric excitation of magnons by three different techniques, parallel pumping, perpendicular pumping in the first-order and in the second-order Suhl processes. The four-magnon interaction is discussed in the third section and shown to have three important effects: saturation of the parametric magnon population; coherence of the parametric magnon states; and nonlinear dynamics. The last section is devoted to study the nonlinear dynamics of parametric magnons that manifests in self-oscillations in the magnon populations and chaotic behavior.