Thermal conductivity measurements on the La-Lu-Tb alloy system show that short-range magnetic order in the magnetic-impurity spin system does not change the superconducting properties in a substantial way. There appears to be no anomaly in the thermal conductivity at the temperature where short-range order occurs. The critical-field curves are depressed far below the prediction of the multiple-pair-breaking theories, and this seems to indicate the presence of a strong exchange-field enhancement.

• Received 30 March 1970

DOI:https://doi.org/10.1103/PhysRevB.2.1287