Micromagnetic Modeling on Current-Induced Multiple Domain-Wall Motion in Permalloy Nanotubes

We performed micromagnetic modeling on moving multiple data bits (2-64 bits) in permalloy (Ni₈₀Fe₂₀) cylindrical nanotubes (PCNTs) and numerically investigated the domain-wall movement, which relies on the applied current, the Gilbert damping factor α, and radii ratio β. It was found that current-driven multiple transverse domain walls (TDWs) motion in nanotubes with an outer diameter below 25 nm and β > 0.33 was characteristic of an exceptional massless mobility. We observed that the velocity of TDWs confined in nanotubes, which was in proportion to the applied current, depended mainly on the sizes of the tubes, and α, but was independent of the number of TDWs. The obtained results offer a way to design the magnetization structures for the DW-based devices by controlling the nanotube geometric and material parameters.