Exotic Transverse-Vortex Magnetic Configurations in CoNi Nanowires

TL;DR

This study reveals complex magnetic vortex configurations in CoNi nanowires, influenced by local structural and chemical variations, combining experimental electron holography with micromagnetic simulations for detailed analysis.

Contribution

It introduces the first detailed analysis of exotic transverse-vortex magnetic states in CoNi nanowires, linking magnetic configurations to local structural and chemical heterogeneity.

Findings

Presence of vortex and axial magnetic domains within single nanowires

Magnetic configurations are influenced by local chemical composition and crystal structure

Micromagnetic simulations confirm experimental observations and elucidate magnetic behavior

Abstract

The magnetic configurations of cylindrical Co-rich CoNi nanowires have been quantitatively analyzed at the nanoscale by electron holography and correlated to local structural and chemical properties. The nanowires display grains of both face-centered cubic (fcc) and hexagonal close packed (hcp) crystal structures, with grain boundaries parallel to the nanowire axis direction. Electron holography evidences the existence of a complex exotic magnetic configuration characterized by two distinctly different types of magnetic configurations within a single nanowire: an array of periodical vortices separating small transverse domains in hcp rich regions with perpendicular easy axis orientation, and a mostly axial configuration parallel to the nanowire axis in regions with fcc grains. These vastly different domains are found to be caused by local variations in the chemical composition modifying the crystalline orientation and/or structure, which give rise to change in magnetic aniso-tropies. Micromagnetic simulations, including the structural properties that have been experimentally determined, allows for a deeper understanding of the complex magnetic states observed by electron holography.