Visualization of the Magnetic Structure of Sculpted
Three-Dimensional Cobalt Nanospirals
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Abstract
In this work, we report on the direct
visualization of magnetic
structure in sculpted three-dimensional cobalt (Co) nanospirals with
a wire diameter of 20 nm and outer spiral diameter of 115 nm and on
the magnetic interactions between the nanospirals, using aberration-corrected
Lorentz transmission electron microscopy. By analyzing the magnetic
domains in three dimensions at the nanoscale, we show that magnetic
domain formation in the Co nanospirals is a result of the shape anisotropy
dominating over the magnetocrystalline anisotropy of the system. We
also show that the strong dipolar magnetic interactions between adjacent
closely packed nanospirals leads to their magnetization directions
adopting alternating directions to minimize the total magnetostatic
energy of the system. Deviations from such magnetization structure
can only be explained by analyzing the complex three-dimensional structure
of the nanospirals. These nanostructures possess an inherent chirality
due to their growth conditions and are of significant importance as
nanoscale building blocks in magneto-optical devices