Study of the Distribution of N2 in Ta and V Using Rotational Hysteresis in the Superconducting Mixed State

Rotational hysteresis curves of selectively oriented single crystals of tantalum and vanadium were determined in the mixed superconducting state at 2°K, as a function of nitrogen content. Enhanced flux pinning, which varied in magnitude with the nitrogen content, was observed when the magnetic field was parallel to the $\text{〈110〉}$ directions in vanadium and the $\text{〈100〉}$ directions in tantalum. These results are consistent with the hypothesis that the nitrogen forms clusters on specific crystallographic planes, determined by the respective elastic anisotropies of the solvent metal.