Nonlinear dynamics of magnetic vortices in single-crystal and ion-damaged N

Nonlinear dynamics of magnetic flux lines in superconducting Nb(Formula presented) are studied using the vibrating-reed technique and a resonance-line-shape analysis. A yield point for plastic deformation of the flux-line lattice is linked to the onset of a dissipation anomaly previously associated with a flux-line lattice melting transition. The resonance (10 kHz range) of radiation-damaged samples bifurcates into patterned sidebands at high drives, with additional nonlinear response emerging above 200 kHz, which may signal the onset of chaos.