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 〈110〉 directions in vanadium and the 〈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.