Low-field peak effect in type II superconductors

The combined effect of a surface (edge) barrier and volume pinning on the dependence of critical current I c on the magnetic field (I⊥H 0) in bulk type II superconductors is investigated. In low magnetic fields, there is a portion of the curve I c(H 0) where I c grows with H 0, causing a nontrivial peak effect in this field range. Such behavior is explained by the combined effect of a surface (edge) barrier and volume pinning, the latter being rather sensitive to the transport current density distribution in a superconductor.