VALENCE-BAND STRUCTURE OF EPITAXIALLY GROWN FE3O4(111) FILMS

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