Current driven domain wall study in U-shape permalloy wire

Current-induced domain wall study in a single layer ferromagnetic U-shape structure is reported. The U-shape Ni₈₀Fe₂₀ permalloy wire, 40 nm thick, 0.5 μm wide and 6 μm long is fabricated by means of electron-beam lithography and lift-off techniques. A maximum magnetic field of 4 kOe is applied and detailed investigations are performed from - to 400 Oe. Results from four-channel dc system measurements reveal the resistance jumps at a critical positive DC current of 1.75 mA in which this jump is found to be irreversible. There is no symmetric jump when a negative DC current is applied. This implies that there is an asymmetric domain wall depinning due to the inclined free energy landscape. The jump of resistance corresponds to the domain wall motion in MFM images. Therefore, high current density replaces the applied field and induces the domain wall motion.