Anisotropy of the penetration depth in superconducting tin

The temperature dependence and anisotropy of the penetration depth $\lambda \mathrm{}\left(T\right)\mathrm{}$ in superconducting tin was measured using a superconducting magnetometer. Single bulk crystals of tin were used as samples to measure the anisotopy with respect to crystallographic orientations. Considerable anisotropy was found with respect to $\hat{j}$, the shielding-current direction, and $\hat{n}$, the direction of the normal to the sample plane surfaces. These data are compared to a simple theory of nonlocal anisotropy. They are also fitted to the BCS theory by varying parameters.