Ferromagnetic resonance (FMR) was used to study the magnetic properties of Fe3O4 films to characterize the Verwey transition. Epitaxial, smooth films were deposited by molecular beam epitaxy. FMR spectra were recorded using a 9.49 GHz Brucker EMX system from room temperature to 80 K with a magnetic field applied perpendicular to the film surface. A single resonance feature was observed above the Verwey transition temperature (T v∼ 105\ K). However below Tv additional features were observed indicating the presence of complex magnetic interactions below T v. © 2013 IEEE.