Direct Measurement of the Temperature-Dependent Magnetic Penetration Depth in Y-Ba-Cu-O Crystals

Abstract

The temperature dependence of the magnetic penetration depth $\lambda$ is determined directly from low-field dc magnetization measurements on single-crystal Y-Ba-Cu-O ($T_c=89.7\mathrm{}$ K, $\Delta T_c=0.2\mathrm{}$ K). The results are consistent with the behavior expected from a BCS ($s$ wave) superconductor.