ANISOTROPY OF THE SIZE EFFECT IN THE ELECTRICAL-RESISTIVITY OF HIGH-PURITY AL SINGLE-CRYSTALS

To clarify the anisotropy of the de size effect in Al, measurements ha ve been made of the electrical resistivity rho(4.2) (K) of high-purity Al single crystals (RRR similar or equal to 50 000) at 4.2 K. The spe cimen surfaces were set parallel to each of three crystallographic pla nes, {100}, {111} and {110}, and the axis orientations were parallel t o [100], [111] and [110]. The main results were the following. (1) The size effect increased in the following order of the surface orientati ons: {110}, {111}, {100}. (2) For the size effect due to a {110} surfa ce, the Fuchs-Sondheimer theory with rho(b)l(b) = 0.82 f Omega m(2) ga ve a good description, while, for the size effect due to {100} and {11 1} surfaces, substantial disagreement with the theory was suggested fo r the very thick specimens. (3) For each surface orientation, rho(4.2 K) for sufficiently thin specimens was independent of the axis orienta tion within the experimental error; i.e. the size effect was independe nt of the direction of current flow. (4) However, as the specimen thic kness increased, strong anisotropy of rho(4.2) (K) with respect to the current direction appeared: rho(4.2 K) increased in the following ord er of directions: [110], [111], [100]. Results (3) and (4) suggest an anisotropy effect of the bulk resistivity rho(b) in high-purity Al.