Magnetic states in wide annular structures

The results of nonintrusive high-resolution imaging of the magnetic states present in wide Co rings with a small inner hole 1.7 m outer diameter, 300 nm inner diameter, and 700 nm width are presented. Rather than the reproducible onion state commonly found in rings, a prevalent triangle state is observed, with other magnetic states characteristic of disks also occurring. The uniformity and the magnetic states in these wide rings are found to be more typical of disks than of rings. Analyzing the energetics of the formation of the magnetic states, this is attributed to the reduced shape anisotropy in wide rings as compared to narrow rings.