Oscillatory dependence of current driven domain wall motion on current pulse length

The aim of the paper is to report on domain wall (DW) motion driven by nanosecond-long current pulses in L-shaped permalloy nanowire fabricated by electron-beam lithography. The nanowires are 40 nm thick, with widths between 100 and 300 nm. In this experiments, a single DW is first nucleated in the bend of the L-shaped wire using a sequence of magnetic fields. The presence of the DW between contacts at either end of the bend is probed by resistance measurements. Owing to the anisotropic magnetoresistance of permalloy, the introduction of a DW is associated with a small decrease of the nanowire´s resistance (about 0.2 Ohm). After the DW has been nucleated, a current pulse with variable amplitude and length. By comparing the resistance of the nanowire before and after the current pulse it can be determined whether the DW has moved out of the bend.