Macrovortex Structure in Hard Superconductors

The magnetization of hard superconducting wires, in the presence of a transverse magnetic field, can be induced to collapse by the application of a small, local field pulse. Under certain conditions the collapse may propagate along the wire in steps, leaving behind a spatially periodic variation in the remanent magnetization of the wire. The remanent magnetization is associated with discrete vortices of wire. A phenomenological explanation for the formation of the macrovortex structure is proposed. According to this explanation, the energy of magnetization, which is initially stored uniformly over a finite volume, is preferentially dissipated locally during the process of flux jumping, thereby raising the temperature of the region to the critical temperature. Although the formation of the macrovortex structure has thus far been observed only in unclad wire of high pinning strength, it represents a potentially important mechanism for the concentration of energy during a collapse of magnetization.