The surface and the internal magnetic structure of bamboo-like cylindrical nanowires with tailored diameter modulations have been determined exploiting the direct photoemission and transmission contrasts using photoemission electron microscopy combined with X-ray magnetic circular dichroism, as well as complementary magnetic force microscopy and micromagnetic simulations. Bamboo-like cylindrical nanowires with diameters of 130 and 140 nm, and a modulation periodicity of 400 nm were electrochemically grown into the pores of alumina templates. FeCoCu and Co nanowires were selected to offer parallel and perpendicular magnetization easy axis, respectively. For FeCoCu nanowires, a main longitudinal magnetization configuration is found consistent with the predominant shape anisotropy. In addition, a weaker modulated contrast along the wires’ axis is observed that matches the position of each diameter modulation: vortex-like structures are observed at the ends of the wires and at the surface around the modulations. In Co nanowires, a multi-segmented vortex-like structure with alternating opposite chirality is found not matching the periodicity of the diameter modulations. Such a spin configuration is interpreted considering that Co nanowires exhibit hexagonal symmetry with c axis nearly perpendicular to the nanowires defining strong uniaxial transverse magnetocrystalline anisotropy.

We report a novel pinning type in modulated nanowires: the “corkscrew”. The magnetization in wide segments forms a skyrmion-tube with a helical core along the nanowire.

A single domain wall (DW) moves at linearly increasing velocity under an increasing homogeneous drive magnetic field. Present experiments show that the DW is braked and finally trapped at a given position when an additional antiparallel local magnetic field is applied. That position and its velocity are further controlled by suitable tuning of the local field. In turn, the parallel local field of small amplitude does not significantly affect the effective wall speed at long distance, although it generates tail-to-tail and head-to-head pairs of walls moving along opposite directions when that field is strong enough.