  The fundamental limits currently faced by traditional computing devices
necessitate the exploration of new ways to store, compute and transmit
information. Here, we propose a three-dimensional (3D) magnetic interconnector
that exploits geometry-driven automotion of domain walls (DWs), for the
transfer of magnetic information between functional magnetic planes. By
combining state-of-the-art 3D nanoprinting and standard physical vapor
deposition, we prototype 3D helical DW conduits. We observe the automotion of
DWs by imaging their magnetic state under different field sequences using X-ray
microscopy, observing a robust unidirectional motion of DWs from the bottom to
the top of the spirals. From experiments and micromagnetic simulations, we
determine that the large thickness gradients present in the structure are the
main mechanism for 3D DW automotion. We obtain direct evidence of how this
tailorable magnetic energy gradient is imprinted in the devices, and how it
competes with pinning effects due to local changes in the energy landscape. Our
work also predicts how this effect could lead to high DW velocities, reaching
the Walker limit during automotion. This work provides new possibilities for
efficient transfer of magnetic information in three dimensions.
