Graphene oxides (GO) have been widely utilized for preparing conductive heterostructures via converting insulating GO back to conductive reduced GO (RGO). Such conversion may substantially impact the results if the introduced heterostructures are sensitive to the conversion processes. To avoid the concerns, herein a novel Fe3O4/graphene (Fe3O4/GN) heterostructure of high electrical conductivity have been prepared by directly using highly conductive GN without any reducing agent or post-treatment. Results of the electrical properties, magnetic properties, complex permittivity and permeability suggest that the Fe3O4/GN interfaces are responsible for the influence of the corresponding properties. The intrinsically conductive features coupled with the Fe3O4/GN interfaces allow the heterostructures to possess sufficient microwave absorption at relatively low filler loading, with tunable effective absorption bandwidth observed over 4-18 GHz. Fundamental mechanisms indicate the advantages of the simple strategies and resulting heterostructures promise a great arena for advanced graphene heterostructures that are not achievable upon RGO. (C) 2015 Elsevier Ltd. All rights reserved.