Current-driven magnetization switching in circular magnetic nanodots

In this paper, the magnetization switching mechanism in circular magnetic nanodots produced by an electrical current applied perpendicular to the dot film plane is studied. Two different dot configurations have been considered: a solid dot (disk) and a dot with a hole in the center (ring). The results show two different switching mechanisms depending on dot diameter and thickness: magnetization rotation for small dimensions and vortex nucleation for bigger dimensions, the threshold size being around 100 nm in diameter and 5 nm in thickness. The switching currents obtained for different dot diameters appear to be very similar. On the contrary the dependence on dot thickness is strong, the switching currents being smaller for thinner dots. (C) 2003 Elsevier B.V. All rights reserved.