Disorder effect and the vortex phase transition in layered organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br

We report systematic detailed measurement of the superconducting properties on the layered organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br near 80 K and the effect of disorder on the superconducting transition temperature Tc. The reversible part of the magnetization (reversible magnetization) and the magnetic entropy change (ΔS) were studied. Using the London model, we determine the temperature dependence of the London penetration depth (λ) from the slope of the linear M(lnH) dependence of the isothermal magnetization. Our results show the strong dependence of ΔS and λ on the temperature. The structural transformation which occurs at the vicinity of 80 K very strongly influences the physics of vortex lattice and the associated magnetic behavior.