Bloch-point-mediated topological transformations of magnetic domain walls in cylindrical nanowires

Cylindrical nanowires made of soft magnetic materials, in contrast to thin strips, host domain walls of two distinct topologies. Following 15 years of theoretical predictions of the unique dynamic features of such walls, such as absence of Walker breakdown, we report on experiments here. Unexpectedly, we evidence the dynamic transformation of topology upon wall motion above a field threshold, a phenomenon that had been previously overlooked. Micromagnetic simulations highlight the underlying phenomenon for one type of transformation, involving the nucleation of a Bloch-point singularity. This calls for reexamining existing predictions, and further experiments to highlight the conditions favoring the transformation.