Excitation and control of large amplitude standing magnetization waves

Abstract

A robust approach to excitation and control of large amplitude standing magnetization waves in an easy axis ferromagnetic by starting from a ground state and passage through resonances with chirped frequency microwave or spin torque drives is proposed. The formation of these waves involves two stages, where in the first stage, a spatially uniform, precessing magnetization is created via passage through a resonance followed by a self-phase-locking (autoresonance) with a constant amplitude drive. In the second stage, the passage trough an additional resonance with a spatial modulation of the driving amplitude yields transformation of the uniform solution into a doubly phase-locked standing wave, whose amplitude is controlled by the variation of the driving frequency. The stability of this excitation process is analyzed both numerically and via Whitham's averaged variational principle.