Nucleation and high-density packing of 360{\deg} domain walls on planar ferromagnetic nanowires by using circular magnetic fields

TL;DR

This paper demonstrates a method to nucleate and densely pack 360-degree domain walls in ferromagnetic nanowires using circular magnetic fields, enabling higher data storage density through micromagnetic simulations.

Contribution

It introduces a novel approach for high-density 360-degree domain wall packing on nanowires using circular magnetic fields and pinning sites, with detailed analysis of their formation and stability.

Findings

Minimum spacing of 240 nm between domain walls

Achieved density of 4 domain walls per micron

Opposite circulation of adjacent 360-degree domain walls

Abstract

We propose a mechanism for nucleation and high-density packing of 360{\deg} domain walls (DWs) on planar ferromagnetic nanowires, of 100 nm width, by using circular magnetic fields. The extent of the stray field from a 360{\deg} DW is limited in comparison to 180{\deg} DWs, which allows them to be packed more densely than 180{\deg} DWs in a potential data storage device. We use micromagnetic simulations to demonstrate high-density packing of 360{\deg} DWs, using a series of rectangular 16 x 16 nm2 notches to act as local pinning sites on the nanowires. For these notches, the minimum spacing between the DWs is 240 nm, corresponding to a 360{\deg} DW packing density of 4 DWs per micron. Understanding the topological properties of the 360{\deg} DWs allows us to understand their formation and annihilation in the proposed geometry. Adjacent 360{\deg} DWs have opposite circulation, and closer spacing result in the adjacent walls breaking into 180{\deg} DWs and annihilating.