Multiphase Fe-oxide thin films are fabricated on glass substrates by a facing-target sputtering technique.X-ray diffraction and X-ray photoelectron spectroscopy reveal that Fe,Fe3O4,γ-Fe2O3 and FeO coexist in the films.High resolution transmission electron microscopy shows the well-defined columnar grain structure with the unoxidized Fe as the core and iron-oxide as the shell.The low-field positive and high-field negative magnetoresistances coexist in such a system at room temperature,which can be explained by considering a shell/core model.Nonlinear current-voltage curve and photovoltaic effect further confirm the tunneling-type conduction.