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 $\sim 2.6$ 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.