Magnetization evolution in a Permalloy dot driven by spin-polarized currents in multi-nanocontact geometry

Abstract

Magnetization evolution in a Permalloy dot with radius R=200nm and thickness L=10nm driven by spin polarized currents was studied by micromagnetic simulations with three point contacts on a diameter. We obtained rich phase diagrams through changing the directions, magnitudes and the inter-distances of the spin-polarized currents. The current must exceed a minimum value before changes in the magnetic state occurred. As the current density was increased, the ground state changed from a single vortex state to complex magnetic states via nucleation and annihilation of vortex–antivortex pairs. However, these rich magnetization phases finally recovered into two different stable vortex states after the current was powered off.