Magnetic domain-wall velocity oscillations in permalloy nanowires

Oscillations of the field-driven domain-wall (DW) velocity in permalloy nanowires are observed above the Walker breakdown condition using high-speed magneto-optic polarimetry. A one-dimensional analytical model and numerical simulations of DW motion and spin dynamics are used to interpret the experimental data. Velocity oscillations are shown to be much more sensitive to properties of the DW guide structure (which also affect DW mobility) than the DW spin precessional frequency, which is a local property of the material. The results demonstrate the feasibility of experimentally probing the complex field-driven DW dynamics in magnetic nanowires, thereby testing the validity of theoretical models and numerical simulations that describe the dynamics.