«Exotic Transverse-Vortex Magnetic Configurations in CoNi Nanowires»
Ingrid Marie Andersen, Luis Alfredo Rodríguez, Cristina Bran, Cécile Marcelot, Sébastien Joulie, Teresa Hungria, Manuel Vázquez, Christophe Gatel and Etienne Snoeck
ACS Nano, December 11, 2019
DOI: https://doi.org/10.1021/acsnano.9b07448
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 anisotropies. 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.
This work derives from the current collaboration between our GNMP group and CEMES – CNRS, Toulouse, France. It has been partly supported by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO) under project MAT2016-76824-C3-1-R and by the Regional Government of Madrid under project S2018/NMT-4321 NANOMAGCOST-CM