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

TL;DR

This paper investigates the topological transformations of magnetic domain walls in cylindrical nanowires, revealing experimental evidence of dynamic topology changes involving Bloch points and highlighting discrepancies with simulations.

Contribution

It provides the first experimental evidence of topology transformations in magnetic domain walls involving Bloch points in cylindrical nanowires.

Findings

Experimental evidence of topological transformations upon wall motion

Micromagnetic simulations show precessional dynamics involving Bloch points

Discrepancy between simulations and experiments in reverse transformation

Abstract

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.