Magnetization switching modes in nanopillar spin valve under the external field

The current-induced magnetic switching is studied in Co/Cu/Co nanopillar with an in-plane magnetization traversed under the perpendicular-to-plane external field. Magnetization switching is found to take place when the current density exceeds a threshold. By analyzing precessional trajectories, evolutions of domain walls and magnetization switching times under the perpendicular magnetic field, there are two different magnetization switching modes: nucleation and domain wall motion reversal; uniform magnetization reversal. The first mode occurs at lower current density, which is realized by the formation of the reversal nucleus and domain wall motion; while the second mode occurs through complete magnetization reversal at higher current density. Furthermore, the switching time reduces as the spin-polarized current density increases, which can also be grouped into two reversal modes.