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

Olivier Fruchart, A Wartelle, B Trapp, M Staňo, Christophe Thirion, S Bochmann, J Bachmann, M Foerster, L Aballe, O. Menteş, A Locatelli, A Sala, L Cagnon, J. -C Toussaint

Published 2018-06-28Version 1

Cylindrical nanowires made of soft magnetic materials, in contrast to thin strips, may host domain walls of two distinct topologies. Unexpectedly, we evidence experimentally the dynamic transformation of topology upon wall motion above a field threshold. Micromagnetic simulations highlight the underlying precessional dynamics for one way of the transformation, involving the nucleation of a Bloch-point singularity, however, fail to reproduce the reverse process. This rare discrepancy between micromagnetic simulations and experiments raises fascinating questions in material and computer science.