Reduction of Threshold Current Density for Current-Driven Domain Wall Motion using Shape Control

We investigated the aspect ratio (thickness/width) dependence of the threshold current density required for current-driven domain wall (DW) motion in Ni 81 Fe 19 nanowires. It has been shown theoretically that the threshold current density is proportional to the product of the hard-axis magnetic anisotropy K ⊥ and the DW width λ [G. Tatara and H. Kohno: Phys. Rev. Lett. 92 (2004) 086601]. We show experimentally that K ⊥ can be controlled by the magnetic shape anisotropy in the case of Ni 81 Fe 19 nanowires, and that the threshold current density increases as K ⊥ ·λ increases. We succeeded in reducing the threshold current density by half using the shape control.