Metastable magnetic domain walls in cylindrical nanowires

• Published in: Journal of magnetism and magnetic materials 2015-05, Vol.381, p.457-462
• Main Authors: Ferguson, C.A., MacLaren, D.A., McVitie, S.
• Format: Article
• Language: English
• Subjects: Domain wall; Domain wall structure; Domain walls; Ground state; Magnetic domains; Magnetic nanotubes; Magnetic nanowires; Nanotubes; Nanowires; Permalloy; Phase diagram; Spin structure; Walls
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2015.01.027

The stability of the asymmetric domain wall (ATDW) in soft magnetic cylindrical nanowires and nanotubes is investigated using micromagnetic simulations. Our calculated phase diagram shows that for cylindrical permalloy nanowires, the transverse domain wall (TDW) is the ground state for radii below 20nm whilst the Bloch point wall (BPW) is favoured in thicker wires. The ATDW stabilises only as a metastable state but with energy close to that of the BPW. Characterisation of the DW spin structures reveals that the ATDW has a vortex-like surface spin state, in contrast to the divergent surface spins of the TDW. This results in lowering of surface charge above the critical radius. For both cylindrical nanotubes and nanowires we find that ATDWs only appear to exist as metastable static states and are particularly suppressed in nanotubes due to an increase in magnetostatic energy. [Display omitted] •We simulate the micromagnetic structures of domain walls in cylindrical nanowires.•A phase diagram identifies ground and metastable states.•Asymmetric transverse walls are metastable in nanowires but suppressed in tubes.•Unrolling surface magnetisation aids visualisation of asymmetry and chirality.•We predict experimental discrimination based on magnetic charge distribution.