title: Observation of a bi-domain state and nucleation free switching in mesoscopic ring magnets.
abstract: We present the results of a study of the magnetic properties of an array of 34-nm thick Co(100) epitaxial ring magnets, with inner and outer diameters of d(in) = 1.3 microm and d(out) = 1.6 microm, respectively. Magnetic measurements and micromagnetic simulations show that a two step switching process occurs at high fields, indicating the existence of two different stable states. In addition to the vortex state, which occurs at intermediate fields, we have identified a new bi-domain state, which we term the onion state, corresponding to opposite circulation of the magnetization in each half of the ring. The onion state is stable at remanence and undergoes a simple and well characterized nucleation free switching.
authors.affiliation: Cavendish Laboratory, University of Cambridge, United Kingdom.
authors.forename: J
authors.initials: J
authors.lastname: Rothman
authors.forename: M
authors.initials: M
authors.lastname: Kläui
authors.forename: L
authors.initials: L
authors.lastname: Lopez-Diaz
authors.forename: C A
authors.initials: CA
authors.lastname: Vaz
authors.forename: A
authors.initials: A
authors.lastname: Bleloch
authors.forename: J A
authors.initials: JA
authors.lastname: Bland
authors.forename: Z
authors.initials: Z
authors.lastname: Cui
authors.forename: R
authors.initials: R
authors.lastname: Speaks