Direct imaging of phase relation in a pair of coupled vortex oscillators

Andreas Vogel,Markus Weigand,André Drews,Guido Meier

doi:10.1063/1.4771683

Abstract

We study the magnetization dynamics in a stray-field coupled pair of ferromagnetic squares in the vortex state. Micromagnetic simulations give an idea of the mediating stray field during vortex gyration. The frequency-dependent phase relation between the vortices in the spatially separated squares is studied using time-resolved scanning transmission x-ray microscopy while one element is harmonically excited via an alternating magnetic field. It is shown that the normal modes of coupled vortex-core motion can be understood as an attractive (low-frequency) and a repulsive (high-frequency) mode of the effective magnetic moments of the microstructures.

Highlights

Due to potential applications in new concepts of high-density and ultrafast nonvolatile data storage devices,[1,2,3,4,5] information-signal processing devices,[6,7] logical units,[8,9,10] and microwave emission sources,[11,12] the dynamic properties of ferromagnetic micro- and nanostructures have gained a broad scientific interest
It has been shown that the resonance frequency of vortices is strongly influenced by the strength of the magnetostatic interaction given by the distance between the elements and the relative configuration of the core polarizations, i.e., the directions of the out-of-plane magnetization components
Stray-field coupled vortex gyrations in a pair of ferromagnetic elements have been demonstrated via time-resolved magnetic transmission x-ray microscopy,[27,28,29] time-resolved photoemission electron microscopy,[30] and electrical measurements.[31,32]

Summary

Introduction

Due to potential applications in new concepts of high-density and ultrafast nonvolatile data storage devices,[1,2,3,4,5] information-signal processing devices,[6,7] logical units,[8,9,10] and microwave emission sources,[11,12] the dynamic properties of ferromagnetic micro- and nanostructures have gained a broad scientific interest. Andreas Vogel,1,a Andre Drews,[1,2] Markus Weigand,[3] and Guido Meier1 1Institut fur Angewandte Physik und Zentrum fur Mikrostrukturforschung, Universitat Hamburg, 20355 Hamburg, Germany 2Arbeitsbereich Technische Informatik Systeme, Universitat Hamburg, 22527 Hamburg, Germany 3Max-Planck-Institut fur Intelligente Systeme, 70569 Stuttgart, Germany (Received September 2012; accepted November 2012; published online 5 December 2012)

Results

Conclusion