Inductive measurements ofUPt3in the superconducting state

The inductive response of several ${\mathrm{UPt}}_3$ samples obtained from four different materials-fabrication groups has been measured from 50 to 700 mK at frequencies varying between 32 Hz and 33 MHz. The temperature dependence of the penetration depth, λ(T), is presented for each sample. The low-frequency (≤4.7 kHz) data suggest a linear temperature dependence of λ(T/${\mathit{T}}_{\mathit{c}}$≤0.5) for the samples possessing a double feature near the superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$. We have verified that this double feature present in λ(T) for some of the samples corresponds to the double jump observed in the specific heat. On the other hand, λ(T/${\mathit{T}}_{\mathit{c}}$≤0.5) is found to have a quadratic temperature dependence for unannealed specimens which exhibit only a single transition at ${\mathit{T}}_{\mathit{c}}$. The linear temperature dependence of λ(T) is consistent with the presence of line nodes in the basal plane, while the quadratic dependence found for other samples suggests that impurity scattering dominates in these specimens. The double transition in λ(T) has been studied in magnetic fields up to 1.6 T, and the resulting phase diagram is consistent with the one constructed from thermodynamical measurements. The high-frequency (≥3 MHz) data suggest λ(T/${\mathit{T}}_{\mathit{c}}$≤0.5)∝${\mathit{T}}^{\mathrm{\eta }}$, where 2≤η≤4. The possible origins of the frequency dependence of λ(T) are discussed, as well as the effect of the surface quality on η.