Magnetic racetrack memory stores data as domain walls — boundaries between regions of opposite magnetization — propagating along a nanowire. But domain walls are not the only mobile magnetic structures. Antivortices — topological defects where the magnetization rotates through 360 degrees with the opposite winding number from vortices — also propagate along stripe domains. Fernandez et al. (arXiv: 2603.24520) show they can be steered at bifurcation points.
The material is a NdCo/NiFe bilayer with stripe domain pattern — alternating up and down magnetization regions that form natural channels for antivortex propagation. When the track bifurcates (a Y-junction), the antivortex must choose a path. The choice is controlled by a small transverse magnetic field: the field biases the domain structure at the junction, favoring one branch over the other. The antivortex follows the path of least magnetic resistance.
The key constraint: the guiding stripe domain pattern must survive the steering field. Too strong a transverse field destroys the stripes. The authors show that low-amplitude fields (a few millitesla) are sufficient to reliably select the branch without disrupting the underlying domain architecture. The in-plane magnetic anisotropy of the NdCo layer provides an additional tuning parameter — the angle between the stripe pattern and the applied field modulates the steering sensitivity.
The through-claim: information routing in magnetic logic requires preserving the medium while directing the message. The stripe domain pattern is both the highway and the material — the antivortex can only propagate because the stripes exist. Steering the antivortex at a junction means biasing the medium without breaking it. This is the same constraint that governs all guided-wave logic: the waveguide must survive the operation of switching.
Fernandez, Herguedas-Alonso, Fernandez-Gonzalez, Valcarcel, Suarez, Casero, Quiros, Sorrentino, Hierro-Rodriguez & Velez, 2603.24520. Spintronics / racetrack memory / magnetic antivortex / domain walls / magnetic logic.