QUANTUM-WELL AND TIGHT-BINDING ANALYSES OF SPIN-POLARIZED PHOTOEMISSION FROM AG FE(001) OVERLAYERS/

Spin-polarized photoemission experiments on expitaxial Ag overlayers o n, Fe(001) have shown that a minority-spin surface state of the bare s ubstrate evolves into an interface state, moves to higher energies, an d crosses the Fermi level E(F) between 3 and 4 Ag monolayers. Applicat ion of a phase accumulation model shows that this state is a quantum-w ell (QW) state characterized by the quantum number v = 1, where v = m - n, and where n and m are the number of wave-function nodes and numbe r of layers, respectively. Higher members of the QW series cross E(F) with a periodicity DELTAm = (1-k(F)/k(BZ))-1 identical with that in re cent theories for the alternation between ferromagnetic and antiferrom agnetic coupling in magnetic multilayers. The QW model fails at low co verages. A tight-binding model captures the behavior at low coverages while reproducing QW behavior at high coverages.