Upper Critical Fields of Ba2YCu3O9-δ

Abstract

The temperature dependence of the upper critical field H _c2 of the high T _c superconductor Ba₂YCu₃O_9-δ was measured resistively between 0 and 40 T on a single phased sample with T _c=92 K. The critical field defined as the midpoint of the transition reaches 34 T at the boiling point of liquid-nitrogen. From the initial slope of the H _c2(T) curve of - 1.27 T/K, the electronic specific heat coefficient was estimated to be 7.5 mJ/mol·K² using the dirty limit approximation.