Pumping Effects Contributing to the Excitation of Phonon Instabilities in Ferromagnetic Insulators

Abstract

A survey is made of mechanisms contributing to the excitation of phonon instabilities in ferromagnetic insulators. The distinction between the morphic and intrinsic dependence of elastic stiffness on the direction of magnetization is discussed, and conclusions are drawn about the relative importance of morphic and intrinsic pumping effects. Transverse and parallel magnetoelastic pumping effects are described, and a theory of transverse magnetoelastic pumping is developed for both cubic and uniaxial crystals. An estimate of the transverse magnetoelastic pump threshold for Zn₂Y is given.