Interfacial structure, magnetic and transport properties of the (Fe3O4)(1-x)(SrTiO3)(x) composite films prepared by cosputtering were investigated systematically. X-ray diffraction, scanning electron microscopy and transmission electron microscopy analyses indicate that the nanosized Fe3O4 grains embedded in amorphous SrTiO3 matrix with well-defined interfaces. The X-ray photoelectron spectroscopy and zero-field-cooling and field-cooling curves reveal that the composite films have very light interfacial diffusion. The composite films exhibit room temperature ferrimagnetism and enhanced resistivity with increasing x. The tunneling transport of the conduction electrons across the grain boundaries causes negative-tunneling magnetoresistance of 6.9% for x = 0, and 3.3% for x = 0.13 at 50 kOe. (C) 2013 Elsevier B. V. All rights reserved.