Magnetization reversal process in elongated Co rings with engineered defects

Abstract

We report a significant modification of the magnetization reversal process in thin film rings with engineered defects created by a focused ion beam. Using magnetic force microscopy, with in situ in-plane field, we observe that the traditional onion-vortex transition that occurs in defect-free rings can be suppressed, and the reversal instead takes place through domain wall motion. We have also investigated the effects of defect size, location, and distribution on the overall magnetization state. The results are explained in terms of pinning of domain walls by the engineered defects. © 2008 American Institute of Physics.