Vortex edge barriers and critical current density in granular superconductors

Abstract

AbstractType‐II superconductors, even without bulk pinning and in the absence of a macroscopic Bean–Livingston surface barrier for vortex penetration, can exhibit barriers for flux penetration. We investigated some new edge barriers based on the laminar model, that are governed by the anisotropy ratio, grain coupling strength, and grain size. Expressions describing the pinning potential Up and critical current density Jc are derived for magnetic fields near Hc1. It is shown that edge barrier effects play a substantial role in a realistic description of the critical current density for both MgB2 and high‐Tc superconductors.