Magnetite (Fe3O4) thin films have been grown epitaxially on zinc oxide (ZnO) substrates, using reactive molecular beam epitaxy. The film quality was found to be strongly dependent on the oxygen partial pressure during growth. For a uniform Fe3O4 film a certain pressure variation was needed during growth. Structural, electronic, and magnetic properties were analyzed utilizing low energy electron diffraction, Hard X-ray Photoelectron Spectroscopy (HAXPES), Magneto-Optical Kerr Effect (MOKE), and X-ray Magnetic Circular Dichroism (XMCD). Diffraction patterns show clear indication for growth of Fe3O4 in the [111] direction on ZnO(0001). Non-destructive depth profiling by HAXPES revealed uniform magnetite thin films. Both, MOKE and XMCD measurements show easy in-plane magnetization. The dichroic spectra clearly support the formation of Fe3O4. (C) 2011 Elsevier B.V. All rights reserved.