Current-induced domain wall motion in magnetic nanowires with various widths down to less than 20nm

We experimentally and theoretically study the current-induced domain wall motion in magnetic nanowires with various widths, and discuss the issues concerning the domain wall motion in wires with reduced widths down to less than 20 nm. For Co/Ni nanowires, the threshold current density significantly increases as the width decreases below 30nm and the domain wall motion is not observed within the studied current density range for a number of devices with the wire width of around 20 nm. The relationship between the threshold current density and wire width is reasonably reproduced by a theoretical calculation based on the adiabatic spin-transfer torque model. The micromagnetic simulation suggests that high-anisotropy materials are promising for domain-wall-motion devices with wire widths beyond 20 nm.