Micromagnetic modelling of magnetic domain walls and domains in cylindrical nanowires

TL;DR

This paper reviews micromagnetic modelling of magnetic domain walls and structures in cylindrical nanowires, highlighting various types, their dependencies on material and geometry, and recent findings like skyrmion tubes and helicoidal structures.

Contribution

It provides a comprehensive overview of micromagnetic simulations revealing complex magnetic structures and dynamics in cylindrical nanowires, including recent discoveries of skyrmion tubes and topological effects.

Findings

Identification of transverse and vortex domain walls and their transition dependence

High velocities of field or current-driven domain walls in nanowires

Observation of skyrmion tubes and helicoidal structures in larger diameter nanowires

Abstract

Magnetic cylindrical nanowires are very fascinating objects where the curved geometry allows many novel magnetic effects and a variety of non-trivial magnetic structures. Micromagnetic modelling plays an important role in revealing the magnetization distribution in magnetic nanowires, often not accessible by imaging methods with sufficient details. Here we review the magnetic properties of the shape anisotropy-dominated nanowires and the nanowires with competing shape and magnetocrystalline anisotropies, as revealed by micromagnetic modelling. We discuss the variety of magnetic walls and magnetic domains reported by micromagnetic simulations in cylindrical nanowires. The most known domain walls types are the transverse and vortex (Bloch point) domain walls and the transition between them is materials and nanowire diameter dependent. Importantly, the field or current-driven domain walls in cylindrical nanowires can achieve very high velocities. In recent simulations of nanowires with larger diameter the skyrmion tubes are also reported. In nanowires with large saturation magnetization the core of these tubes may form a helicoidal ('corkscrew') structure. The topology of the skyrmion tubes play an important role in the pinning mechanism, discussed here on the example of FeCo modulated nanowires. Other discussed examples include the influence of antinotches ('bamboo' nanowires) on the remanent magnetization configurations for hcp Co and FeCo nanowires and Co-Ni multisegmented nanowires.