Current-assisted magnetization switching in a mesoscopic NiFe ring with nanoconstrictions of a wire

A mesoscopic NiFe ring with nanoconstrictions of a wire was fabricated by electron beam lithography and lift-off techniques. Magnetic switching and reversal process have been measured by magnetoresistance as a function of the applied current. It is shown that the applied current has an effect on the switching fields and finally affects the reversal process. The decrease or increase in the switching field from the vortex state to the onion state depends on the electron flow with respect to the direction of domain propagation. The spin in the ring switches from an onion state to the opposite onion state in the low applied current via the double switching process. However, the spin in the ring switches directly from an onion state to the opposite due to the spin torque effect when the applied current is higher than the critical current density (of 10(7) A/cm(2)). (c) 2006 American Institute of Physics.