Giant flux creep through surface barriers and the irreversibility line in high-temperature superconductors

Magnetic and transport phenomena in high-temperature superconductors due to magnetic flux relaxation and transport over the surface barrier are investigated. Vortex dynamics controlled by the penetration both of pancake vortices and vortex lines is discussed. The penetration field Hp for pancakes decays exponentially with temperature. The size of the magnetization loop is determined by the decay of Hp during the process of relaxation, but its shape remains unchanged. The irreversibility line associated with the pancake penetration is given by Hirr exp(-2T/T0) and may lie both above and below the melting line.