Dissipation near Tc in a textured (Bi,Pb)2Sr2Ca2Cu3Oy, silver-clad tape

Abstract

The transport resistance R of a silver-clad Bi(2223) tape has been studied as a function of temperature T and magnetic field H in the case of the field applied parallel (H∥ab) and perpendicular (H∥c) to the tape plane in the region of temperature near Tc (T/Tc>0.9) and low fields below 2000 G. As observed in the low-temperature and high-field region, the broadening of the resistive transition [Tc(0)-Tc(H)] follows a power-law variation of the field, i.e., [Tc(0)-Tc(H)]∝Hq, where q is about 1/2 from the experimental result. The R(T) curves at various fields show an Arrhenius behavior for both H∥ab and H∥c. However, the activation energy U derived from the slope of the Arrhenius plot is more than one order of magnitude larger than usually reported. We think this large deviation of the U value is from the assumption of temperature-independent U in the Arrhenius law and find that a reasonable U value can be obtained through an improved Arrhenius plot by considering the dissipation as induced by the thermally activated flux flow in the vortex-liquid state. The anisotropy both in magnetoresistance curves R(H) and the irreversibility line Hirr(T) shows a scaling behavior as predicted by the effective-mass model, i.e., f∥c(H)=f∥ab(γH), where f can be either R or Tirr, γ is the anisotropy factor. From the scaling, γ is about 3.5. Such a small γ value for present sample suggests that the dissipation for H∥ab is dominated by the small-angle grain boundaries, as described in the railway-switch model.