Anisotropic magnetic penetration depth of grain-aligned HgBa2Ca2Cu3O8+δ

Abstract

The temperature ($T$) dependence of the anisotropic magnetic penetration depth $\lambda \mathrm{}\left(T\right)\mathrm{}$ of magnetically aligned powders of crystalline $\mathrm{Hg}{\mathrm{Ba}}_2{\mathrm{Ca}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{8+\delta }$ is reported. Measurements were performed in the Meissner state using the ac-susceptibility technique. The temperature dependences of the in-plane, ${\lambda }_{\mathrm{ab}}\mathrm{}\left(T\right)\mathrm{}$, and out-of-plane, ${\lambda }_c\mathrm{}\left(T\right)\mathrm{}$, penetration depths are markedly different. This is believed to arise from the large anisotropy ratio $\gamma =\left[\frac{{\lambda }_c\mathrm{}\left(0\right)\mathrm{}}{{\lambda }_{\mathrm{ab}}\mathrm{}\left(0\right)\mathrm{}}\right]\simeq 30$. The behavior of ${\lambda }_{\mathrm{ab}}\mathrm{}\left(T\right)\mathrm{}$ is indicative of $d$-wave superconductivity while ${\lambda }_c\mathrm{}\left(T\right)\mathrm{}$ is similar to the behavior expected for a superconductor with intrinsic Josephson coupling between the Cu${\mathrm{O}}_2$ planes. Similar measurements were performed on ${\mathrm{Ba}}_{0.6}$ ${\mathrm{K}}_{0.4}$Bi${\mathrm{O}}_3$ powders for comparison.