Nonlinear dynamics of magnetic multilayers. II. Antiferromagnetic interlayer interaction

An essentially nonlinear dynamics with a high level of excitation of a magnetic multilayer consisting of two nanolayers with a nonisotropic antiferromagnetic interaction between the layers is considered. The theoretical study was carried out within the framework of discrete Landau–Lifshitz equations without damping. Exact solutions of this integrable system are obtained for all types of nonlinear excitations. They are reduced to the nonlinear superposition of precessional and nutational oscillations of coupled macroscopic magnetic moments. The dependences of the oscillation frequencies of the moments on the total energy of the system and its magnetization along a preferred axis, which are integrals of motion, are found. In different ranges of values of these integrals, an exact, approximate, and qualitative study of the problem was carried out, which was accompanied by a direct numerical analysis of the initial equations. Attention is drawn to the possibility of significantly different levels of excitations of identical layers. Finding the relationship between the dynamic characteristics of excitations (their frequencies) and their integral characteristics (energy and magnetization) can be useful in studying multilayer systems by resonance methods.