The magnetic and magneto-optical properties of heteroepitaxial magnetite (Fe3O4) thin films were investigated. Of interest was the role of misfit strain on determining its magnetic properties. Epitaxial magnetite thin films were deposited by molecular beam epitaxy using molecular oxygen on (100) oriented SrTiO3. BaTiO3 and MgO. Polar spectroscopic magneto-optic Kerr effect (MOKE) measurements on the thin films over near infrared to visible spectral region revealed two dominant magneto-optical transitions. It is shown that the magnetic and magneto-optical properties depend strongly on misfit strain. The longitudinal MOKE saturation rotation angle decreased with the lattice misfit and was attributed to the formation of antiphase boundaries. Coercivity ranged from 19 to 39 mT and was proportional to the lattice misfit. Thin films were all magnetically isotropic within the plane. The magnetic domain size measured by magnetic force microscopy (MFM) decreased with misfit. (c) 2008 Elsevier B.V. All rights reserved.