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 Ni81Fe19 nanowires. It has been shown theoretically that the threshold current density is K-perpendicular to and the DW width lambda [G. Tatara and H. Kohno: Phys. Rev. proportional to the product of the hard-axis magnetic anisotropy K-perpendicular to Lett. 92 (2004) 086601]. We show experimentally that K-perpendicular to can be controlled by the magnetic shape anisotropy in the case of Ni81Fe19 nanowires, and that the threshold current density increases as K-perpendicular to - lambda increases. We succeeded in reducing the threshold current density by half using the shape control.