Bifurcation analysis of Landau-Lifshitz-Gilbert dynamics under circularly polarized field

Uniform solutions of Landau-Lifshitz-Gilbert equation coupled with magnetos tatic Maxwell equations are discussed in the case where the problem is rota tionally invariant around a certain axis and the external field is circular ly polarized in the perpendicular plane. It is shown that a remarkably rich variety of phase portraits is present in the dynamics, with two or four ti me-harmonic modes rigidly rotating with the field (P modes) and zero, one, or two quasiperiodic modes (Q modes). Different portraits are separated by bifurcation lines of saddle node, Andronov-Hopf, homoclinic-saddle connecti on, and semistable-limit-cycle type. The complete phase portrait and bifurc ation diagram of thin films with negligible crystal anisotropy is presented and discussed. (C) 2001 American Institute of Physics.