Scaling of the vortex-liquid resistivity and temperature and magnetic field dependent activation energy in Ho doped (Bi, Pb)-2212 superconductor

The vortex-liquid resistivity close to the vortex glass to liquid transition region is analyzed in detail for Ho doped (Bi, Pb)-2212 superconductor. A large broadening of resistive transition in magnetic field is observed, which is a direct evidence for the thermal fluctuation in the vortex system, and hence the modified vortex glass to liquid transition theory is used to calculate the temperature and magnetic field dependent activation energy U-0(B,T). The resistivity shows a glassy behavior even at higher temperature and magnetic field for the Ho stoichiometry x=0.075, which is believed to come mainly from the point defect brought about by the doped Ho atoms in the (Bi, Pb)-2212 system. The results also show that the glass transition temperature (T-g), magnetic field dependent activation energy U-0(B), and U-0(B,T) values are maximum for x=0.075, which shows that the flux lines are effectively pinned and the vortices are in glassy state for this sample, and the enhancement due to Ho doping has both scientific and technological importance. Also, the scaling of vortex-liquid resistivity obtained in the presence of magnetic field is quite useful for better understanding of the behavior of the vortex liquid in high temperature superconductors. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3148265]