  Comprehending the interaction between geometry and magnetism in
three-dimensional (3D) nanostructures is of importance to understand the
fundamental physics of domain wall (DW) formation and pinning. Here, we use
focused electron beam-induced deposition to fabricate magnetic nanohelices with
increasing helical curvature with height. Using electron tomography and Lorentz
transmission electron microscopy, we reconstruct the 3D structure and
magnetization of the nanohelices. The surface curvature, helical curvature and
torsion of the nanohelices are then quantified from the tomographic
reconstructions. Furthermore, by using the experimental 3D reconstructions as
inputs for micromagnetic simulations we can reveal the influence of surface and
helical curvature on the magnetic reversal mechanism. Hence, we can directly
correlate the magnetic behavior of a 3D nanohelix to its experimental
structure. These results demonstrate how control of geometry in nanohelices can
be utilized in the stabilization of DWs and control of the response of the
nanostructure to applied magnetic fields.
