Quantum-well and tight-binding analyses of spin-polarized photoemission from Ag/Fe(001) overlayers

Spin-polarized photoemission experiments on expitaxial Ag overlayers on Fe(001) have shown that a minority-spin surface state of the bare substrate evolves into an interface state, moves to higher energies, and crosses the Fermi level EF between 3 and 4 Ag monolayers. Application of a phase accumulation model shows that this state is a quantum-well (QW) state characterized by the quantum number {ν}=1, where {ν}=m-n, and where n and m are the number of wave-function nodes and number of layers, respectively. Higher members of the QW series cross EF with a periodicity {Δ}m=(1-kF/kBZ{)}^{{{-}}1}$ identical with that in recent theories for the alternation between ferromagnetic and antiferromagnetic coupling in magnetic multilayers. The QW model fails at low coverages. A tight-binding model captures the behavior at low coverages while reproducing QW behavior at high coverages.