Simultaneous control of magnetic topologies for reconfigurable vortex arrays

The topological spin textures in magnetic vortices in confined magnetic elements offer a platform for understanding the fundamental physics of nanoscale spin behavior and the potential of harnessing their unique spin structures for advanced magnetic technologies. For magnetic vortices to be practical, an effective reconfigurability of the two topologies of magnetic vortices, that is, the circularity and the polarity, is an essential prerequisite. The reconfiguration issue is highly relevant to the question of whether both circularity and polarity are reliably and efficiently controllable. In this work, we report the first direct observation of simultaneous control of both circularity and polarity by the sole application of an in-plane magnetic field to arrays of asymmetrically shaped permalloy disks. Our investigation demonstrates that a high degree of reliability for control of both topologies can be achieved by tailoring the geometry of the disk arrays. We also propose a new approach to control the vortex structures by manipulating the effect of the stray field on the dynamics of vortex creation. The current study is expected to facilitate complete and effective reconfiguration of magnetic vortex structures, thereby enhancing the prospects for technological applications of magnetic vortices. Arrays of nanomagnets with whirlpool-like spins can now be configured on-demand using simple magnetic-field treatments. Magnetic vortices have been targeted for spintronic logic gates because they offer four states, defined by vortex polarity and circularity, in a single device element. Researchers led by Mi-Young Im from Lawrence Berkeley National Laboratory in the USA have found that fabricating arrays with geometric imperfections – flat edges chopped off otherwise circular nanodisks – enabled control over both the direction the vortices point in and how they whirl. Direct imaging of the arrays using synchrotron X-rays revealed that reversing an applied magnetic field triggered immediate vortex reconfigurations. Stray fields around the asymmetric nanodisks were identified as the key contributors to controlled vortex reversals, and the team's simulations suggest these effects offer possibilities for selective control of individual vortex elements. Selective control of vortex structures in closely packed nanodisks with a robust, yet simple, electrode architecture by applying current through electrode.