Anisotropy of the generalized Ginzburg-Landau parameters chi1 and chi2 in clean, cubic, type II superconductors

From the nonlocal GLAG theory expressions are derived for chi1 and chi2 of a clean, cubic crystal with a general Fermi surface. In the region of weak nonlocality near T/sub c/ the correction terms in H/sub c/2, chi1, and chi2 due to the nonspherical Fermi surface are expressed by two dimensionless Fermi surface averages. For highly purified Nb single crystals and polycrystalline Nb samples, chi1 and chi2 were determined from magnetization measurements in the temperature range (0.3--0.95) T/sub c/. The experimental data show that the orientation dependence in chi2 is twice as large as in chi1, in agreement with the theoretical result near T/sub c/. The two Fermi surface averages that characterize the anisotropy of H/sub c/2, chi1, and chi2 near T/sub c/ are estimated from experimental data for Nb and V