Properties of lithographically formed cobalt and cobalt alloy single crystal patterned media

We have fabricated single crystal cobalt and Co₉₀Cr₁₀ islands of dimension 130 nm×330 nm×20 nm by a direct-write electron beam lithography and ion-milling process. The islands have the crystalline easy axis along the short axis. These islands have been characterized by magnetic force microscope in the presence of an applied field. About 85% of the as-grown cobalt islands were single domain and rest 15% showed a bi-domain state. The as-grown Co₉₀Cr₁₀ islands were all in a single domain state. In remanence all the islands were single domain in both the pure and the alloyed films. Two modes of switching were observed. Some of the islands switched by going through a bi-domain state and the rest switched directly from a single domain state to a single domain state