Excitation and control of large amplitude standing magnetization waves

TL;DR

This paper presents a method to excite and control large amplitude standing magnetization waves in ferromagnets using chirped microwave or spin torque drives, involving resonance passage and phase-locking.

Contribution

It introduces a novel two-stage process for generating and controlling standing magnetization waves through resonance passage and autoresonance in ferromagnetic materials.

Findings

Successful formation of standing waves via resonance passage

Control of wave amplitude through frequency variation

Validation of stability through numerical and analytical methods

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.