Critical Fields of Superconducting Tin, Indium, and Tantalum

Precise ballistic-induction measurements of the critical field curves of tin, indium, and tantalum are reported. The measurements were made to provide more accurate data on the deviation of the critical field curves from the parabolic law. The resulting deviation functions are generally within the range of uncertainty of earlier measurements. The main experimental error in the observed deviation now arises from uncertainty in the extrapolation of the measurements to 0^ from the present lower limit of 1. 1^. Measurements at lower temperatures which will eliminate some of this uncertainty are to be desired.