Magnetization switching in a mesoscopic NiFe ring with nanoconstrictions of wire

Magnetoresistance in a mesoscopic NiFe ring with nanoconstrictions of wire has been measured. For the applied field tilted from the perpendicular direction, it is shown that the applied current has an effect on the switching fields and finally the transition process due to the spin torque effect. 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 magnetization in the ring exhibits only a double switching process at a low applied current. However, when the applied current is higher than the critical current density, the magnetization shows a combination of single and double switching processes. For the applied field direction perpendicular to the wire, an enhancement in magnetoresistance is obtained around zero fields at a low applied current, which is due to the domain wall trapped at nanoconstrictions. Furthermore, it is found that the magnetization in the ring goes via a single onion to onion switching process at whatever value of the applied current. © 2006 American Institute of Physics.