INDUCTIVE MEASUREMENTS OF UPT3 IN THE SUPERCONDUCTING STATE

The inductive response of several UPt3 samples obtained from four diff erent materials-fabrication groups has been measured from 50 to 700 mK at frequencies varying between 32 Hz and 33 MHz. The temperature depe ndence of the penetration depth, lambda(T), is presented for each samp le. The low-frequency (less than or equal to 4.7 kHz) data suggest a l inear temperature dependence of lambda( T/T-c less than or equal to 0. 5) for the samples possessing a double feature near the superconductin g transition temperature T-c. We have verified that this double featur e present in lambda(T) for some of the samples corresponds to the doub le jump observed in the specific heat. On the other hand, lambda(T/T-c less than or equal to 0.5) is found to have a quadratic temperature d ependence for unannealed specimens which exhibit only a single transit ion at T-c. The linear temperature dependence of lambda(T) is consiste nt with the presence of line nodes in the basal plane, while the quadr atic dependence found for other samples suggests that impurity scatter ing dominates in these specimens. The double transition in lambda(T) h as been studied in magnetic fields up to 1.6 T, and the resulting phas e diagram is consistent with the one constructed from thermodynamical measurements. The high-frequency (greater than or equal to 3 MHz) data suggest lambda(T/T-c less than or equal to 0.5)proportional to T-eta, where 2 less than or equal to eta less than or equal to 4. The possib le origins of the frequency dependence of lambda(T) ale discussed, as well as the effect of the surface quality on eta.