The Fermi surfaces of Cu-Pd alloys studied by positron annihilation

The Fermi surfaces of Cu-Pd alloys below 63% Pd are studied by means of the angular correlation of positron annihilation with crossed- and long-slit geometries. The <001>- and <110>-radii decrease with increasing palladium content up to 30% in agreement with a calculation based on the rigid band model. The <111> neck radius also decreases with increasing composition, and it is suggested that the Fermi surface detaches from the hexagonal face of the Brillouin zone around 20% Pd, but remains to bulge in this direction at higher compositions. No detectable change is found in the correlation curves of the ordered and disordered states at 15 and 19% Pd. The origin of stabilization of the long period ordered structure near Cu3Pd is discussed in the light of the present results. (auth.)