Flux closure structures in cobalt rings

Measurements are reported on the magnetization reversal in submicron magnet ic rings fabricated by high-resolution electron beam lithography and lift-o ff from cobalt thin films. For all dimensions investigated, with diameters of 300-800 nm and a thickness of 10-50 nm, the flux closure state is the st able magnetization configuration. However, with increasing diameter and dec reasing film thickness a metastable near single domain state can be obtaine d during the reversal process in an in-plane applied field.