The Fermi Surfaces of Cu–Pd Alloys Studied by Positron Annihilation

Abstract

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 - and -radii decrease with increasing palladium content up to 30% in agreement with a calculation based on the rigid band model. The 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 Cu 3 Pd is discussed in the light of the present results.