Resonant domain wall depinning induced by oscillating spin-polarized currents in thin ferromagnetic strips

The interaction between ac spin-polarized electrical currents and a domain wall initially trapped on a notch in a thin Permalloy nanostrip is investigated by micromagnetic modeling as well as a one-dimensional model that considers the wall as a rigid object. A systematic study of the depinning transition from the notch is carried out in the frequency domain for several static magnetic fields and ac's, both at zero and at room temperature. Due to the resonant amplification of the domain wall oscillations, both the depinning current and the static magnetic field can be significantly reduced with respect to the dc case, and even at room temperature the probability of the domain wall depinning abruptly changes in a narrow frequency range. These observations suggest a low-operation and highly selective mode for further spintronic devices based on domain walls. On the other hand, our analysis is also used to estimate the effective value of the nonadiabatic parameter by direct comparison with recent experiments.