MAGNETIZATION MEASUREMENTS IN THE 80 K TRANSFORMATION FOR DEUTERATED ORGANIC SUPERCONDUCTOR κ-(BEDT-TTF)2Cu[N(CN)2]Br

In this paper, we report systematic magnetic measurements on deuterated organic superconductor (kappa-D-8-Br)kappa-(BEDT-TTF)(2)Cu[ N(CN)(2)]Br. The irreversibility line H-irr(T) and the critical current density J(c) were studied. Our results show the strong dependence of H-irr(T) and J(c) on the cooling rate. The structural transformation which occurs at the vicinity of 80 K very strongly influences the physics of vortex lattice and the associated magnetic behavior. The irreversible magnetization becomes null at H-irr and vortices are not pinned; therefore they can displace more freely for an increase of the field or the temperature.