ISSN:
1573-7357
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract The effect of the reduction in mean free path on the anisotropy of the upper critical fieldH c2 has been studied in Nb by adding Ta and Mo as impurities. It is found that impurities suppress the degree of anisotropy, in qualitative accord with the theory of Hohenberg and Werthamer, which shows that in cubic materials with a nonspherical Fermi surface anisotropy arises from nonlocal corrections to the GLAG theory. The results were analyzed by fitting the observed anisotropy curves to an expansion in Kubic harmonics. It is found that the second harmonic coefficientA 2, which depends on first nonlocal corrections, decreases initially with addition of Ta or Mo according to theory, but tends to level off to an approximately constant value in the dirty limit, where it should vanish. The value of the third harmonic coefficientA 3, which depends on higher-order nonlocal terms, vanishes rapidly with the addition of impurity, the rate of decrease being more rapid for Mo. It is also found that the presence of an impurity does not affect the temperature dependence ofA 2 for both Nb-Ta and Nb-Mo systems andA 3 for the Nb-Ta system and has an approximately similar effect as for pure Nb.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00661184
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