Weak coupling and anisotropy in the magnetic penetration depth of the high-temperature superconductor Tl2Ca2Ba2Cu3O10+δ

Abstract

Magnetic penetration depths λ(T) have been determined as a function of temperature T for the high-temperature superconductor ${\mathrm{Tl}}_2$ ${\mathrm{Ca}}_2$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{10+\mathrm{\delta }}$. Magnetization measurements were performed on an aligned, composite powder sample (${\mathit{T}}_{\mathit{c}}$=123 K) with the magnetizing field parallel or perpendicular to the common c axes of the dispersed crystallites. The magnetization in the vortex state was analyzed using the theory of Kogan et al. [Phys. Rev. B 38, 11 958 (1988)] to obtain values for λ. The results were best described by BCS weak-coupling theory in the clean limit, with deduced values λ(0) of 173 and 480 nm for the components of the penetration-depth tensor.