Fe films were deposited on either a heated GaAs(1 0 0) substrate at 200 degreesC or a GaAs(1 0 0) substrate with a 5 Angstrom Au buffer layer in ultrahigh vacuum by molecular beam epitaxy. In order to understand the influence of the heating process and the buffer layer on the magnetic properties, spin polarisation of secondary electrons was investigated. Photoelectron spectroscopes of Fe 3p, Ga 3d and As 3d core levels were used as tools to explain the magnetic behaviour. It is found that according to preparation processes, the magnetic properties of the Fe/GaAs(1 0 0) samples could be due to either the formation of FeGaAs compounds or superparamagnetism in the first several monolayers (MLs). Furthermore. neither treatment greatly improved sample properties. (C) 2002 Elsevier Science B.V. All rights reserved.