Effect of magnetic field direction on the remanent resistance levels and vortex chirality of a multilayered magnetic ring

The effect of applied field direction on the magnetoresistance response of a 5 mu m diameter Co/Cu/NiFe thin film ring has been examined. When the Co layer of the ring is placed in a vortex state, four possible remanent magnetization configurations exist, in which the NiFe layer is in one of four states: forward onion, reverse onion, clockwise vortex or counterclockwise vortex. The resistance levels of these four remanent states depend on the field angle with respect to the electrical contact leads, and measured values agree well with an electrical model. The chirality of the Co vortex can be determined from measurements of the minor loop, and the chirality of the NiFe vortex can be set using two-step field cycling at two different field angles.