Analysis of High-Power Effects in Ferrimagnetics from the Point of View of Energy Transfer. Part I. First-Order Instabilities

Abstract

Spin‐wave instabilities in ferrimagnetics in the past have usually been analyzed by considering the perturbed equations of motion of the normal variables of the spin system. In this paper the spin‐wave behavior is analyzed without the use of the normal mode development. The properties of the kth spin wave—its energy and the phases and amplitudes of its transverse magnetization components—are derived using real variables exclusively. Then the criteria for all the first‐order instability thresholds are derived from the power balance of the spin system. The physical processes which lead to spin‐wave instabilities are discussed.