DEPENDENCE ON FERMI-SURFACE DIMENSIONS OF OSCILLATORY EXCHANGE COUPLING IN CO/CU1-XNIX(110) MULTILAYERS

A significant change in the oscillatory exchange coupling corresponding to the contraction of the Fermi surface in the spacer layers is found in the Co/Cu1-xNix (110) system. The oscillation period becomes longer with increasing Ni concentration: from 12 angstrom (0% Ni) to 23 angstrom (35% Ni). This change manifests that the long-period oscillation across Cu-Ni (110) arises from the singularity at the neck orbit of the spacer Fermi surface. The neck diameters estimated from the measured periods are in good agreement with those of bulk Cu-Ni Fermi surfaces.