Peak effect, vortex-lattice melting line, and order-disorder transition inconventional and high-T-c superconductors - art. no. 184514

We investigate the order-disorder transition line from a Bragg glass to an amorphous vortex glass in the H-T phase diagram of three-dimensional type-I I superconductors taking into account both pinning-caused and thermal fluct uations of the vortex lattice. Our approach is based on the Lindemann crite rion and on results of the collective pinning theory and generalizes previo us work of other authors. It is shown that the shapes of the order-disorder transition line and the vortex-lattice melting curve are determined only b y the Ginzburg number. which characterizes thermal fluctuations, and by a p arameter which describes the strength of the quenched disorder in the flux- fine lattice. In the framework of this unified approach we obtain the H-T p hase diagrams for both conventional and high-T-c superconductors. Several w ell-known experimental results concerning the fishtail effect and the phase diagram of high-T-c superconductors are naturally explained by assuming th at a peak effect in the critical current density versus H signalizes the or der-disorder transition line in superconductors with point defects.