Magnetic Vortex Domain Wall Observation on Polycrystalline Imperfect Iron−Cobalt Alloy Nanowires Growing on 1050 Aluminum

• Published in: Physica status solidi. A, Applications and materials science Vol. 219; no. 5
• Main Authors: Londoño-Calderón, César Leandro, Londoño-Calderón, Alejandra, Moscoso-Londoño, Oscar, Galindo, Arturo, Ponce, Arturo, Pampillo, Laura Gabriela, Martínez-García, Ricardo, José Yacamán, Miguel, Knobel, Marcelo
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-03-2022
• Subjects: Aluminum; Aluminum base alloys; Anisotropy; Arrays; Cobalt base alloys; Coercivity; Crystal defects; Crystallites; Diameters; Domain walls; electron holography; FeCo; Holography; Inclination angle; Iron; low-purity aluminum; Magnetic measurement; Magnetic properties; Magnetic saturation; Magnetization; nanowire arrays; Nanowires; Polycrystals; Remanence; Vortices
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.202100265

Herein, the magnetic vortex domain wall structure of polycrystalline imperfect iron−cobalt alloy nanowires (Nws) growing on 1050 aluminum by pulsed electrodeposition is reported. The magnetic properties are analyzed using magnetometry and off‐axis electron holography. The electrodeposited Nw arrays show homogeneous elemental composition and exhibit a structure composed of piled‐up grains of small crystallites. The saturation magnetization, coercive field, and reduced remanence, measured in directions parallel and perpendicular to the Nw's axis, are studied as a function of the temperature. Although the array of Nws on anodized aluminum grows both straight and within an inclination angle, in both cases, a high shape anisotropy is noticed, which is the most predominant contribution to the magnetic behavior. Misalignments and defects of the Nws in the array, as well as the wide distribution of lengths and diameters, do not contribute significantly to coercivity dispersion. A modified model is used to explain the changes in the magnetic behavior of the Nw's arrays, which accounts for structural imperfections and magnetostatic interactions. The reversal magnetization arising from the vortex domain wall propagation via localized curling is verified by off‐axis electron holography.
Polycrystalline, defective Fe67Co33 arrays of nanowires (Nws) are synthesized from low‐purity anodized aluminum oxide by pulse electrodeposition. The magnetic properties are found to be dominated by shape anisotropy, despising the bending of the nanochannels forming hemispheric cavities. Off‐axis electron holography confirms the magnetization reversal mechanism by vortex domain wall propagation via localized curling.