Magnetic penetration depth of oxygen-deficient YBa2Cu3O7- single crystals (Tc=66 K)

Abstract

For single crystals of YBa2Cu3O7- with Tc=66 K, we measured the magnetic penetration depth ab(T), with the applied magnetic field oriented perpendicular to the CuO2 planes, using high-field magnetization isotherms M(H,T). The zero-temperature value ab(0) is about 2600, a value almost twice that of YBa2Cu3O7- with Tc=90 K, but similar to that of Bi2Sr2CaCu2O8+. The temperature dependence of ab(T) reveals some deviation from the theoretical BCS weak-coupling clean limit, and from the two-fluid model. These observations are discussed and compared with magnetic-penetration-depth data for other high-Tc superconductors. © 1991 The American Physical Society.