Upper Critical Field of High Temperature Superconductors.

摘要

Resistive and magnetic measurements of the superconducting transition in good quality single crystals of YBa sub 2 Cu sub 3 O/sub 7/minus/delta/ and La/sub 2/minus/x/Sr/sub x/CuO sub 4 and in good polycrystalline samples of Ba/sub 1/minus/x/K/sub x/BiO sub 3 are used to derive the temperature dependence and anisotropy of the upper critical field. Comparison of the results shows several common features, most notably the existence of upward curvature in the temperature dependence of the upper critical field. The definition of T/sub c/ from resistance curves and the origin of the upward curvature in the upper critical field are discussed. (ERA citation 14:012365)