The Verwey transition of the Fe3O4 surface studied by ion scattering spectroscopy

The energy spectra of 5.5 keV He+, Ne+, Ar+ and Kr+ ions, scattered from a natural surface of a single crystal of magnetite Fe3O4, have been measured by ion scattering spectroscopy in the temperature range of 95-300 K. The scattered ion yields R+(T) show a deep minimum around 120 K followed by a small maximum around 135 K, i.e. around the Verwey transition temperature of the bulk, corresponding to the disorder-order transition of the distribution of Fe2+ and Fe3+ ions in octahedral sites of the spinel structure. The results are interpreted in terms of the neutralization probability affected by the change of the density of states near the Fermi level, by the change of the electron localization degree as well as of the target material transparency. The anomalies in the R+(T) curve was partly suppressed by a thin film of condensed xenon gas on the target surface. (C) 1999 Elsevier Science B.V. All rights reserved.