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 fails to explain several key experimental results published in the literature. From a careful analysis of these results we conclude that the Flux Line Lattice (FLL) does not melt along a material- and sample-dependent boundary $H_j(T)$ but the opposite, it de-couples from the superconducting matrix becoming more ordered. When the FLL depinning is sharp, the difference between the equilibrium magnetization $M_{eq}(T,H)$ of the pinned and unpinned FLL leads to the observed step-like change $\Delta M_{eq}(T,H)$. We demonstrate that the experimentally obtained $\Delta M_{eq}(T,H)$ can be well accounted for by a variation of the pinning efficiency of vortices along the $H_j(T)$ boundary. 
Y. Kopelevich and P. Esquinazi