Chumak O. Instability of the mixed state of hard superconductors and features of dynamics magnetic flux

The work is devoted to solving the problem of instability of the critical state of hard superconductors. The problem of the critical state stability of a bilayer type-II superconductor, whose layers have different physical properties (critical current density, specific heat, and critical temperature) was solved. In the event of instability of a critical state in a superconducting YBa2Cu3O7−δ single crystal and filling it with magnetic flux, an induction-current model of the inversion of the magnetic moment of the sample is proposed, a transformation of the induction pattern in the material due to a giant thermomagnetic avalanche is schematically constructed. The rough magnetic flux fronts and induction contours in a long hard type-II superconducting cylinder were emulated using the elliptic critical-state model. The solutions of the forced oscillations of the single elastic vortex line have been analyzed considering different affecting on movement forces: pinning, elasticity, viscosity and Lorenz force. Also vortex inert properties due to the different mechanisms of massiveness have been taken into account.