Renormalization of the magnon-phonon interaction in HCP ferromagnets

Abstract

A systematic scheme, based upon Roth linearization of many-body equations of motion (see abstr. A37193 of 1968) is applied to decoupling of the coupled spin-lattice equations of motion of magnetostrictive HCP ferromagnets. Magnetoelastic coupling is characterized by the same microscopic Hamiltonian that gives rise to macroscopic magnetostrictive properties, and magnon-phonon coupling is expressed in terms of macroscopic magnetostriction parameters. Both one- and two-ion magnetoelastic coupling is included through the Evenson and Liu local-strain theory (see abstr. A24313 of 1969). The magnitude of the splitting of magnon and phonon dispersion curves is proportional to appropriate magnetostriction constants divided by the square root of the magnetization, and Jensen's results (see abstr. A13393 of 1972) are recovered in the zero temperature limit.