Fermi Surfaces of Copper-Aluminum Alloys by Positron Annihilation

A novel technique in positron annihilation (J. Phys. Soc. Japan 20 (1965) 1533, 21 (1966) 1947) enabled us to survey the Fermi surfaces of the α-phase alloys in the system Cu-Al. The results were as follows: 1. The neck radius does not increase monotonically with increasing content of Al, but shows an oscillatory behaviour having a maximum at 2∼3 at.% Al and a minimum at 5∼6 at.% Al. 2. For the alloys containing Al more than about 10 at.%, the necks protrude beyond the hexagonal zone faces. 3. The Fermi surface swells out gradually in the <200>-directions with the addition of Al atoms. 4. A possible model of the Fermi surface was proposed for 10.6 at.%-alloy by taking account of four angular-correlation curves corresponding to different orientations of crystals.