Increase in period of oscillatory coupling in Cu by doping with Ni

The origin of oscillatory interlayer coupling via Cu is explored in sputtered Co/Cu multilayer by varying the hole concentration in the copper layers by doping with elements of different valence. Detailed studies were carried out for a series of Cu-Ni alloys. The oscillation period of pure Cu is observed to increase monotonically with increasing Ni concentration and is almost doubled for 40 atomic % Ni. The increase in oscillation period can be accounted for by considering changes in the topology of the Fermi surface of the alloy resulting from the change in band filling.