Purity dependence of the anisotropy of residual electrical resistivity in high-purity Al single crystals

Measurements have been made on the anisotropic dependence of the bulk residual resistivity ρ b at 4.2 K on the current direction in Al single crystals with a {110} main surface. In specimens with RRR≃10000, the anisotropy of ρ b is relatively weak, but shows a fine structure that corresponds to the detailed structure of the Fermi surface of Al: ρ b rises nearly in the direction in which the Fermi surface intersects the Brillouin zone boundary. As the purity level of the specimens increases, the degree of anisotropy increases markedly and the behavior of its own changes. In specimens with RRR≃100000, ρ b increases monotonically in the order of the [110], [111] and [001] directions: the values along [001] and [111] are about 75 and 30 % larger than that along [110], respectively. In the [001] direction, the second-zone Fermi surface is nearest to the zone boundary.