Ratchet Effect of Domain Wall Motion by GHz AC Magnetic Field in Asymmetric Sawtooth-Shaped Ferromagnetic Nanowires

We have investigated a ratchet effect of magnetic domain wall in asymmetric sawtooth-shaped ferromagnetic nanowires under high frequency AC magnetic fields by means of micromagnetic simulation. The ratchet phenomenon has been intensively examined during the domain wall propagation with variation of the asymmetric sawtooth geometry of nanowires as well as variation of the AC external field frequency/strength. Very interestingly, it has been found that there is a strong correlation between the spatial frequency of asymmetrical notches and the effective driving frequency/strength of AC external fields. It is demonstrated that number of notches swept by domain wall ratchet motion per each half-cycle of the driving frequency is controlled under a GHz AC driving field.