Magneto-optical studies of field-driven propagation dynamics of domain walls in permalloy nanowires and scaling of magnetic energy losses in permalloy films and microstructures

The magneto-optical Kerr effect is used to study the propagation dynamics of field-driven magnetic domain walls in Permalloy nanowires. The domain wall velocity- field characteristic is found to be linear below a threshold field and highly non-linear above the threshold. An analytical model is proposed for the propagation dynamics of domain walls in ferromagnetic nanowires at low fields. The magnetic energy loss in Permalloy thin films and microstructures driven by sinusoidal magnetic fields is studied as a function of the applied field frequency over a wide range of frequencies. The magnetic energy loss is shown to be constant at low frequencies and rapidly increasing at higher frequencies. The measurements are found to be in agreement with a model of magnetization reversal based on domain wall motion.