CONSTRAINTS ON THE TEMPERATURE-DEPENDENCE OF THE MAGNETIC PENETRATION DEPTH OF SUPERCONDUCTING BI2SR2CACU2O8+X FROM MEASUREMENTS OF THE LOW-TEMPERATURE SPECIFIC-HEAT

Abstract

We have measured the low-temperature (2-10 K) specific heat of polycrystalline Bi2Sr2CaCu2O8+x in zero applied field and in an applied magnetic field of 1 T. We find no field-induced enhancement of the specific heat, to within the 1% resolution of our calorimeter, in a field of 1 T up to 10 K, in contrast to the YBa2Cu3O7-delta system. The results suggest that the enhancements which have been observed in the specific heat result from a temperature dependence of the pinning of vortices in the mixed state. In analyzing our data, we use a model for the enhancement of the specific heat, and find quantitative agreement. Using this model, we place constraints on the allowed temperature dependence of the ab-plane magnetic penetration depth.