INDUCTIVE MEASUREMENTS AND STUDY OF THE UPPER CRITICAL-FIELD IN UBE13SINGLE-CRYSTALS AS A FUNCTION OF FIELD ORIENTATION

Using sensitive mutual induction techniques, we have measured the real part of the susceptibility, chi'(B,T), and the imaginary part, chi '' (B,T), for three UBe13 single crystals below 1 K and in fields up to 8 T oriented along the [100] and [110] directions, with particular emph asis on the region near the zero-field critical temperature T-c. In th is regime and within our experimental uncertainties of 0.5 mK and 5 mT , no anisotropy was observable for any of the samples. For all three s amples, the magnetic susceptibility between 4 and 15 K was measured an d subtle features were found for two of the samples around 10 K. For o ne of these specimens, an anomaly in chi'(B,T) was observed below the superconducting transition and is likely due to flux pinning mechanism s. The B-c2(T) phase diagrams are presented and compared to the result s of other workers. Finally, the temperature dependence of the penetra tion depth for 0.1 less than or equal to T/T-c less than or equal to 0 .5 was found to be close to T-3, independent of field orientation, and these data are presented and discussed.