Vortex Dynamics in Percolative Superconductors Containing Fractal   Clusters of a Normal Phase
  The effect of fractal clusters on magnetic and transport properties of percolative superconductors is studied. The superconductor contains percolative superconducting cluster carrying a transport current and clusters of a normal phase. It is found that normal phase clusters have essential fractal features. The fractal dimension of the boundary of normal phase clusters is estimated. The current-voltage characteristics of superconductors containing fractal clusters are obtained. It is found that the fractality of the cluster boundary intensifies pinning. This feature permits to enhance the current-carrying capability of the superconductors. 
Yuriy I. Kuzmin