Magnetic phase diagram of type-II superconductors: From high T-c to low T-c superconductors

Phase diagram of both high temperature superconductors and low temperature superconductors are studied within the Ginzburg-Landau approach. Due to enhanced thermal fluctuation strength, disorder effects are relatively small in high T-c superconductors and consequently can be studied analytically. The vortex glass transition line is different and well separated from both the melting line and from the so-called second peak lines. On contrary, in low temperature superconductors, the disorder effect is dominant, as the thermal fluctuation strength is very small. Peak effect appears due to cross over of the collective pinning region to stronger pinning region. The location of the peak effect is obtained. The disorder and thermal fluctuation effects on structure phase transition are also studied. (C) 2008 Elsevier B.V. All rights reserved.Physics, AppliedSCI(E)EICPCI-S(ISTP)