Vortex-glass transformation within the surface superconducting state of β-phase Mo1-xRex alloys

We have performed an experimental study on the temperature dependence of electrical resistivity rho(T) and heat capacity C(T) of the Mo1-xRex (x = 0.20, 0.25) alloy superconductors in different magnetic fields. In the presence of applied magnetic field, the electrical resistivity of these alloys goes to zero at a temperature well above the bulk superconducting transition temperature obtained with the help of heat capacity measurements in the same magnetic field. Our study indicates the presence of a surface superconducting state in these alloys, where the flux lines are pinned in the surface sheath of the superconductor. The configuration of the flux lines (two-dimensional pancake-like) in the surface sheath is understood in the realm of the flux-spot model. Experimental evidence in support of the surface mixed-state state or 'Kulik vortex-state' and the occurrence of a vortex-liquid to vortex-glass transition is presented.