Rigorous dynamic analysis of exchange-coupled films

Abstract

The Landau-Lifshitz equation for distributed film systems, which has been formulated by Chang, Lin, and Priver, is applied to analyze both the quasistatic and dynamic magnetization reversal in exchange-coupled films. Each elementary layer of infinitesimal thickness is assumed to reverse magnetization by coherent rotation, subject to both magnetostatic and exchange forces of the other layers. As an example, detailed analysis is made on "dual uniaxial films," which consist of two uniaxial films of different anisotropy fields in intimate contact, and with their easy axes in parallel. Numerical solutions are obtained for magnetization distribution and switching modes, as functions of film parameters and driving fields. Unique in dual uniaxial films, simultaneous switching, sequence-field switching, and separate switching occur in films with strong, moderate, and weak exchange couplings respectively. A convenient method of constructing the critical curves and a comprehensive classification of switching characteristics are given. Finally, a critique is made of Goto's quasistatic analysis based on lumped-constant approximation. © 1969 The American Institute of Physics.