Topological Control of Magnetic Textures*

We report a topological mechanism to stabilize magnetic textures, such as a vortex structure, in a permalloy disk. The topology in the disk is set by four permalloy ellipsoids surrounding the disk. We introduce a discretized formulation of the winding number to identify the nature of the topology, associated with different magnetic configurations, in the surrounding ellipsoids.
We experimentally show that the less energetically favorable antivortex can be stabilized in a permalloy disk– if the appropriate topological conditions are set. Additionally, we use micromagnetics to simulate a device containing two disks, sharing a common ellipsoid, with each disk surrounded by three additional ellipsoids. We find that in a coupled system, the magnetic texture stabilized in each disk is directly correlated with the winding number in the surrounding ellipsoids.
In summary, our work builds upon existing literature, while consolidating the role of topology in stabilizing magnetic structures. The idea to use a discrete form of winding number is novel, and that topology need not be a phenomenon solely associated with continuous films.