Enhancement of vortex liquid phase and reentrant behavior in NiBi_(3) single crystals

Abstract

We investigate the vortex phase diagram of needle shaped high quality NiBi3 single crystals by transport measurements. The current is applied along the crystalline b-axis of this intermetallic quasi-1D BCS superconductor. The single crystals show a Ginzburg-Levanyuk (G (i)) parameter of about 10(-7), larger by two orders of magnitude than G _(i) in elemental low T_(c) BCS superconductors. Vortex phase diagram, critical currents and pinning forces have been extracted from the experimental data. We observe (i) an enhancement of the vortex liquid phase, (ii) a reentrance of the liquid phase at low fields and (iii) an unusual magnetic field dependence of the pinning force. We suggest that these phenomena result from the interplay between pinning due to quenched disorder and the quasi-1D character of the material which could lead, for instance, to more complex pinning mechanisms at play.