Transport measurements, vortex dynamics and anisotropy in artificially layered (BaCuO sub(2)) sub(2)/(CaCuO sub(2)) sub(2) superconducting films

摘要

In this paper, we present some transport measurements on artificially layered (BaCuO sub(2)) sub(2)/(CaCuO sub(2)) sub(2) superlattices, engineered by the pulsed laser deposition (PLD) technique, and having critical temperatures (zero resistance) of about 80 K. The experimental current-voltage characteristics are discussed in the frame of current-induced unbinding of thermally created vortex-antivortex pairs (in zero-field) and in the frame of vortex glass (VG) transition for fields up to about 10 kG. The transport critical current density is estimated and compared to values reported from magnetization measurements. The field dependence of the activation energy of vortices in the vortex liquid (VL) phase shows a strong effective pinning, due to the high disorder intrinsic to these artificially layered superconductors, at low magnetic fields, and a transition to a thermally activated plastic motion of an entangled VL in higher fields. From the temperature and field orientation dependencies of the vortex melting field, an anisotropy factor of about 20 is estimated for these superlattices.