Nanoscale switch for vortex polarization mediated by Bloch core formation in magnetic hybrid systems.

Phillip Wohlhüter,Georg Heldt,Laura Jane Heyderman,Matthew Thomas Bryan,Sebastian Gliga,Jörg Raabe,Anna Kinga Suszka,Peter Warnicke,Gino Hrkac,Christoforos Moutafis,Stephanie Elizabeth Stevenson,Lalita Saharan,Thomas Thomson,Rajesh Vilas Chopdekar

doi:10.1038/ncomms8836

Abstract

Vortices are fundamental magnetic topological structures characterized by a curling magnetization around a highly stable nanometric core. The control of the polarization of this core and its gyration is key to the utilization of vortices in technological applications. So far polarization control has been achieved in single-material structures using magnetic fields, spin-polarized currents or spin waves. Here we demonstrate local control of the vortex core orientation in hybrid structures where the vortex in an in-plane Permalloy film coexists with out-of-plane maze domains in a Co/Pd multilayer. The vortex core reverses its polarization on crossing a maze domain boundary. This reversal is mediated by a pair of magnetic singularities, known as Bloch points, and leads to the transient formation of a three-dimensional magnetization structure: a Bloch core. The interaction between vortex and domain wall thus acts as a nanoscale switch for the vortex core polarization.

Highlights

Vortices are fundamental magnetic topological structures characterized by a curling magnetization around a highly stable nanometric core
We elucidate the influence of the magnetic domains in the Co/Pd multilayer on the vortex core dynamics and show that the reversal is a complex three-dimensional process mediated by the formation of a magnetic discontinuity that connects two Bloch points, which we call a Bloch core
To investigate the dynamics in the hybrid system, we fabricated square thin film structures consisting of a 50 nm thick Permalloy (Py) layer with 3 mm and 5 mm side length deposited on top of a Co/Pd multilayer (Fig. 2a)

Summary

Introduction

Vortices are fundamental magnetic topological structures characterized by a curling magnetization around a highly stable nanometric core. Imaging the out-of-plane component of the magnetization of the Py layer reveals the vortex core and the presence of an imprinted maze domain state (Fig. 2d).

Results

Conclusion