Valence-band structure of epitaxially grown Fe3O4(111) films

It has recently been shown that well-ordered Fe3O4(111) films can be prepared epitaxially on clean Pt(111) surfaces; various techniques have indicated that these multilayer films are chemically identical to bulk single crystals. We have studied the electronic structure of such an ordered Fe3O4(111) film using angle-resolved photoemission in conjunction with synchrotron radiation. The valence-band structure along the Gamma(L) symmetry line and the resonant emission enhancement across the Fe 3p-->3d excitation threshold have been examined in detail both above (at 300 K) and below (at 90 K) the Verwey transition temperature (similar to 120K) for magnetite. The observed band dispersion agrees reasonably well with band-structure calculations for the high-temperature phase, particularly near the Fermi level, suggesting that Fe3O4, should be treated with band theory. Subtle differences in the valence-band structure are observed between the two temperatures, which may be attributed to a structural change and/or a charge ordering associated with the Verwey transition. The resonant behavior shows, however, no temperature dependence, indicating that resonant photoemission in Fe3O4 remains a localized process and is not influenced by the Verwey transition.