Upper Critical Fields of Amorphous Bi and Bi–Pb Alloys

抄録

The previously measured H_c2(T) in amorphous pure Bi, Bi₇₅Pb₂₅, Bi₅₀Pb₅₀ and Bi₃₀Pb₇₀ showed the upward deviation from the dirty limit values predicted by the Werthamer-Helfand-Hohenberg theory. The strong coupling effect was taken into account at that time for this enhancement of H_c2(T), but it has recently been shown that the distribution of electrical diffusivity might be important and intrinsic in these metastable phases. Our experimental results are reexamined on the basis of this model, that is, the enhancement of H_c2(T) is caused by the inhomogeneous spatial distribution of electrical diffusivity. It is found that the amorphous Bi–Pb system has the similar distribution of electrical diffusivity, while the amorphous pure Bi has a different one.