Resonant Domain Wall Dynamics in a Three-Dimensional Magnetic Nano Double Helix.

Abstract

The extension of magnetic nanostructures to three dimensions (3D) has been predicted to result in phenomena such as non-reciprocal collective dynamics and ultra-fast motion of textures. However, while first indications of dynamics in 3D have been explored in microstructures, the experimental investigation of magnetization dynamics in complex-shaped 3D nanostructures remains challenging. Here, 3D nanoprinted cobalt double-helix nanostructures are investigated with time-resolved X-ray microscopy at nanoscale spatial and picosecond temporal resolution to study their magnetization dynamics. Within the helices, the dynamics of coupled domain walls are observed, and a clear resonant response identified. Micromagnetic simulations confirm that the experimentally observed resonance arises from a harmonic oscillatory mode of the coupled domain walls and predict additional higher-frequency modes, revealing a rich dynamic spectrum. By systematically varying the helix geometry in simulations, we find that the resonant modes can be engineered. This geometrical control promises an alternative to conventional tuning strategies based on tailored magnetic anisotropies, DC bias, or externally applied fields. Together, these experimental and simulated results of magnetization dynamics in complex 3D nanostructures provide a pathway for programmable functionalities, relevant for potential technologies including information processing architectures based on tunable spin texture dynamics.