Anomalous Temperature Dependence of H_c1 in High-T_c Superconductor YBa₂Cu₃O_7-δ

Abstract

Temperature dependence of magnetization curves was measured on a polycrystalline sample of high- T c superconductor YBa 2 Cu 3 O 7-δ . The lower critical field obtained from the magnetization curves has an anomalous temperature dependence, which may infer that a dimensional crossover occurs as observed in an artificial layered superconductor Nb/Cu.