Current driven domain wall motion in magnetic U-pattern

We have studied the current induced domain wall motion by using patterned U geometry. The observation of two magnetic states of the U-pattern was evidenced. One is the vortex domain wall at the center of semicircular arc in U-pattern and the other is the continuous magnetic state without wall. We investigated the influence of the positive and negative dc current injection on domain wall motion before switching field with density on the order of ∼107A∕cm2. The critical current varied dramatically as the bias field is close to the switching field and only gradually as the field is far away from the switching field.