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We report on a comprehensive study of the magnetic properties of the super-conductor vanadium. Starting from a high-purity sample (RRR=1900), we use magnetization measurements to evaluate the primary superconductive parameters of vanadium and their impurity dependence up to a?3.1. For the clean limit we findTc0=5.47 K and ?0=0.78. From the impurity dependence of the transition temperature an rms gap anisotropy of ˜16% is obtained. Furthermore, for Ginzburg-Landau parameters ?1.5 an attractive flux line interaction is found. The experiments on Hc2 anisotropy show results comparable to those for niobium, i.e., a slow decrease of the anisotropy coefficient a4 with increasing impurity parameter and a much faster decrease of the 1=6 component. A detailed analysis of these results awaits further progress of theory.

We report on an evaluation ofHc2 anisotropy effects in arbitrary planes and directions of cubic superconductors. Using Mercator projections, information on the three-dimensional variation ofHc2 is obtained. The results are discussed for the three main crystallographic planes of the cubic lattice and evaluated in terms of their usefulness for an accurate experimental determination of the anisotropy coefficientsA1. Although some planes show interesting features because of special symmetry conditions, we conclude that careful measurements in the (110) plane represent the optimum choice for an accurate determination of the anisotropy coefficients.

Systematic experiments on the impurity and temperature dependence of the Hc2anisotropy in niobium are reported. A combined evaluation of these two dependences within the framework of a recent nonlocal theory is shown to permit a separation of different sources contributing to the Hc2anisotropy. Whereas the l = 4 component of the anisotropy is mainly due to band-structure anisotropies of the normal state, the l = 6 component in pure niobium originates predominantly from anisotropies of the energy gap. The rms anisotropy of the energy gap in niobium is estimated to be 0.08. The anisotropy of the flux line lattice predicted on the basis of the microscopic anisotropy parameters as deduced from the Hc2measurements is in agreement with experimental observations.