title: Large Hysteresis effect in Synchronization of Nanocontact Vortex Oscillators by Microwave Fields.
abstract: Current-induced vortex oscillations in an extended thin-film with point-contact geometry are considered. The synchronization of these oscillations with a microwave external magnetic field is investigated by a reduced order model that takes into account the dynamical effects associated with the significant deformation of the vortex structure produced by the current, which cannot be taken care of by using the standard rigid vortex theory. The complete phase diagram of the vortex oscillation dynamics is derived and it is shown that strong hysteretic behavior occurs in the synchronization with the external field. The complex nonlinear nature of the synchronization manifests itself also through the appearance of asymmetry in the locking frequency bands for moderate microwave field amplitudes. Predictions from the reduced order model are confirmed by full micromagnetic simulations.
authors.affiliation: University of Naples Federico II, Department of Electrical Engineering and Information Technology, I-80125 Naples, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Perna
authors.affiliation: University of Salamanca, Department of Applied Physics, Salamanca, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Lopez-Diaz
authors.affiliation: University of Naples "Parthenope", Department of Engineering, I-80143 Naples, Italy.
authors.forename: M
authors.initials: M
authors.lastname: d'Aquino
authors.affiliation: University of Naples Federico II, Department of Electrical Engineering and Information Technology, I-80125 Naples, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Serpico