Vortex lattice depinning vs. vortex lattice melting: a pinning-based explanation of the equilibrium magnetization jump

In this communication we argue that the Vortex Lattice Melting scenario fai ls to explain several key experimental results published in the literature. From a careful analysis of these results we conclude that the Flux Line La ttice (FLL) does not melt along a material- and sample-dependent boundary H -j(T) but the opposite, it decouples from the superconducting matrix becomi ng more ordered. When the FLL depinning is sharp, the difference between th e equilibrium magnetization M-eq(T, H) of the pinned and unpinned FLL leads to the observed step-like change M-eq(T, H). We demonstrate that the exper imentally obtained Delta M-eq(T, H) can be well accounted for by a variatio n of the pinning efficiency of vortices along the H-j(T) boundary. (C) 2000 Elsevier Science Ltd. All rights reserved.