CRITICAL FIELDS OF NB3AL1-X GE X ALLOYS IN LIQUID H2

Critical field HC2 vs temperature measurements have been completed in pseudo-binary,1 β-W structure, Nb 3Al1-xGex (0.25≤x≤0.3) compounds with both contactless rf and transverse dc resistance measurements. Extrapolation of HC2(T) vs T above 20 kG yields TC=20.7°K. This T C is confirmed by zero-field specific heat measurements.2 HC2(T) vs T is almost linear from TC to 14°K, indicating that paramagnetic limiting is almost completely suppressed. H C2(14°K) ≃200 kG is observed for the TC=20. 7°K material. Extrapolated HC2(0) values are deduced from the high-T data and compared with other physical parameters of the earlier T C=20.05°K superconducting materials.3 These new superconducting materials show potential compared with V3Ga and Nb3Sn, particularly in the liquid-H2 temperature range, if practical wires can be developed. A brief summary of the properties of these alloys was presented at the Eleventh International Conference on Low Temperature Physics4 and more detailed results will be published elsewhere. © 1969 The American Institute of Physics.