Fe on Au(100): Quantum-well states down to a monolayer

Quantum-well states are observed for Fe films embedded in Au(100) using inverse photoemission. They can be analyzed with a simple interferometer model, using bulk states from the ${\mathrm{\Gamma }}_{12}$ ${\mathrm{\Delta }}_1$ ${\mathit{H}}_{15}$ band that are modulated by an envelope function with wavelengths in the order of 7–10 atomic layers (10–14 Å). These states can be followed down to a monolayer, where two states are seen at 0.6 and 1.9 eV. They are tentatively assigned to the ${\mathrm{\Delta }}_5$↓ monolayer state and a ${\mathrm{\Delta }}_1$ quantum-well state. The resulting ferromagnetic exchange splitting of the ${\mathrm{\Delta }}_5$ is 2.7 eV, exceeding the splitting of 1.8–2.1 eV for the analogous bulk band.