Dependence on Fermi surface dimensions of oscillatory exchange coupling in Co/${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Ni}}_{\mathit{x}}$(110) multilayers

A significant change in the oscillatory exchange coupling corresponding to the contraction of the Fermi surface in spacer layers is found in the Co/${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Ni}}_{\mathit{x}}$(110) system. The oscillation period becomes longer with increasing Ni concentration: from 12 Å (0% Ni) to 23 Å (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.