Magnetization and Flux Line Lattice in Anisotropic Superconductors

Abstract

The anisotropies observed in magnetic properties such as the upper critical field, the magnetization and the correlation between the flux line lattice and the crystal lattice are considered in superconductors with uniaxial and cubic symmetry. The magnetization and the correlation are well explained by the effective mass model in uniaxial materials. As far as cubic materials are concerned, the correction of the order parameter to Abrikosov’s solution turns out to be important. The upper critical field for polycrystalline samples is obtained by taking this correction into account. The term which is responsible for the correction of the order parameter plays an essential role in determining the anisotropy of magnetization and the correlation between the flux line lattice and the crystal lattice. The anisotropy of magnetization is in agreement with experimental observations, while the variety of correlations observed in Nb and Pb alloys cannot be explained by the extension of the Ginzburg- Landau equations, which includes only the lowest order term of non-locality.