Quantum Well States and Short Period Oscillations of the Density of States at the Fermi Level in Cu Films Grown on fcc Co(100)

Quantum well states are observed around the ``neck'' of the Fermi surface in Cu films grown on magnetic fcc Co(100) substrates, using high-resolution angle-resolved photoemission. The observation is only possible with an abrupt, nonreacted Cu/Co interface, which is produced by low temperature deposition of the first Cu layer. The analysis of the spectra gives a periodic crossing of the Fermi level of ~2.6 atomic layers, the same short magnetic coupling period obtained in Co/Cu/Co trilayers, and also the same value predicted by the theory. This is a strong confirmation of the role of quantum well states as mediators of magnetic coupling in superlattices.