The electrical resistivity, heat capacity, superconducting upper critical magnetic field and magnetic susceptibility of NiBi 3 have been measured for the polycrystal and needle crystal. The temperature dependence of the resistivity ρ(T ) above the superconducting transition temperature can be explained by the parallel resistor formula. From ρ(T ), using the sum of two GruneisenBloch functions, we have obtained that the lower main value of the Debye temperature is 70 K and the higher one is 300 K. This is compatible with ω E ≡ 30.6 K and ω D ≡ 141 K obtained from the heat capacity using the hybrid Einstein-Debye model. We have compared the angular dependence of the critical magnetic field with that of the effective mass model and found an anisotropic mass ratio m b /m ⊥b ≈ 0.17 for the needle ( b-axis) crystal. Almost the same value of 0.14 is also obtained from the analysis of ρ(T ).

No abstract

The results of studies on superconductor-insulator transitions are reported for Mo and MoRu films of varying thickness deposited on SiO underlayers and on bare glass. The film samples were quench-condensed on glass substrates held at liquid He temperatures. MoRu films on SiO, which offer the most homogeneous film morphology, showed a critical sheet resistance of transition, R c , of ∼6.7 k . Both series of Mo films on SiO and MoRu films on bare glass had R c 13 k . These values are larger than those previously reported for MoGe, MoSi, and MoC films. For the above films in the insulating region far from the transition, the exponent of the thermally activated resistance ranged from 0.5 to 1.0.

No abstract